# How to make home-made calcium blocks for tortoises (Recipe!)



## biochemnerd808

Tortoises need *calcium* in order to build strong bones, a strong shell, and healthy organs. Ideally, they are fed a widely varied diet of nutritious weeds and dark leafy greens that have high levels of bio-available calcium in them. Adding a sprinkling of a healthy plant-based supplement such as TNT can help significantly. However, sometimes a tortoise's calcium requirements go beyond what is found in the plants we can provide.
Some tortoise keepers rely on *sprinkling calcium powder* on tortoise food. However, this has the danger of causing a dosage beyond what a tortoise needs, and may actually cause health problems. For this reason, I like to provide healthy tortoises with calcium sources that they can help themselves to, as needed. Tortoises seem to have a good instinct about when their body needs more calcium.





*Cuttlefish bone* (found in the bird aisle of most pet stores, or available in bulk online) is a good option. However, not all tortoises seem to care for cuttlebone. *Quarry chalk* is a good source of calcium. It is widely available in the UK and some other countries, but is hard to come by here in the US. Finally, *man-made calcium blocks* are another good source of calcium. Some such products are available in the pet trade. However, I have found them to be _ridiculously expensive_, and they often have _undesirable ingredients_such as sugar or artificial dyes and flavors. For this reason, I did a little research, and decided to try making my own calcium blocks. 




_The home-made calcium blocks are tortoise-approved!
_
After seeing how ridiculously easy it is to make the home-made calcium blocks, I wanted to share the recipe and procedure with you, so that you and your tortoise(s) may benefit from it as well.

First, you need to decide on the calcium source. *Food-grade calcium carbonate*(CaCO3) is one good option, sometimes called Limestone flour. Another, more affordable and more easily available source is so called *Agricultural Lime* (CaCO3) - I got it at our local feed store for $8 for a 50lb bag! Agricultural lime is produced by pulverizing limestone or chalk, and is commonly used as a soil amendment. Please make sure to read the label CAREFULLY: you want to make sure that it not so-called hydrated lime, that it does not contain Magnesium Carbonate, and that it does not have any other ingredients and impurities in significant amounts. Here is the kind I bought:




_One of many good options
_
The only other ingredient you will need to make lime blocks is water.
For tools, you will need:


a large mixing bowl
a *sturdy* spoon to mix with
and some kind of mold that will withstand 200 degrees F (93 degrees C). I used a silicone muffin pan that I got at Goodwill for $2
an oven, pre-heated to 200 degrees F (93 degrees C)

It took a little bit of mixing and adding to find just the right consistency. Here is the ratio of ingredients that I found to work best:

1.5 cups of warm water (H2O)
7 cups of CaCO3 powder (Ok, sue me; I used a liquid measuring cup to measure the dry powder, which I know is a no-no in cooking... but in this case it worked fine, since I was just aiming for keeping track of the ratio that worked)





First, I measured the Calcium Carbonate Powder into the mixing bowl. Then I made an indentation into the powder, and slowly poured the warm water into it. Then I very carefully stirred the mixture, to minimize clouds of powder flying up and all around. The mixture quickly gets very thick, so you really do need a sturdy spoon made of metal or wood. A spatula didn't cut it.




_Yum! Calcium paste!
_
Keep on mixing until there is no more liquid on top, and no more pockets of powder at the bottom. It will get progressively tougher to mix, and will start looking like mortar or thick plaster of Paris.

Next, spoon the Calcium Carbonate + water mixture into the molds you have chosen. The amount I made was exactly the right amount to fill all 12 wells of the muffin pan, plus 1 small cup.

_*NOTE*: Please DO NOT dump excess slurry down your drain. It can clog your drain and/or wreck your in-sink disposal. I took the bowl outside and hosed it down. It is perfectly safe just to dump it onto your garden or your lawn. 
In fact, if you don't have a lot of tortoises, and don't want to have the remnants of a 50lb bag (minus 7 cups) of agricultural lime sitting in your garage... just spread the rest into your lawn, or dig it into your flower beds or raised garden beds!_





Next, carefully place the mold into the oven. I used a cookie sheet under the silicone muffin pan since it is a bit wobbly. Set the timer to 1 hour.





After 1 hour of baking, open the oven door and carefully pull the oven rack out far enough that you can safely touch the calcium cakes. You will notice that water has risen to the top of them. Use a paper towel or napkin to wick off the excess liquid. This will significantly cut down on the drying time.
Bake for another 2-3 hours, depending on your oven. I checked every hour to remove more liquid, and after a total of 4 hours, they looked completely dry, and had shrunken in the molds.

Carefully remove the mold(s) from the oven, and place somewhere to cool down. This took a long time. I used our handy dandy infrared thermometer to check the temperature of the calcium blocks, and waited for them to almost be cool enough to touch.
Once they are cool enough, carefully remove each calcium block from the mold, and place it on a cookie drying rack. They should come out easily. I let them sit like that overnight, just to make sure all the moisture had dried out.





The next day, I put one of these beautiful calcium cupcakes into each of the tortoise enclosures, and packed the extra ones into ziploc bags for later use. Within minutes of placing the cakes into the enclosures, the tortoises congregated around them, and took a few nibbles. Pretty soon, they were sporting cute little calcium mustaches...




_Jill approves.
_
The part that really made my day: Amber, my XXL female Russian tortoise had just laid eggs. She has been stubbornly refusing to eat cuttlefish bone, and does not eat weeds if I have sprinkled them with calcium. However, by evening, her calcium cake looked like this:





I hope you have fun making your own calcium blocks, and that your tortoises enjoy them as much as mine do! Please keep in mind that in order to properly absorb calcium, a tortoise needs UVB to produce vitamin D3. You can read a little more about this HERE.

By the way, I copied this article from my tortoise blog, if you are interested in reading more.

Ps: When you mist your enclosures, please avoid spraying the calcium cakes too thoroughly (you might take them out briefly), because otherwise they may disintegrate.

Pps: You might experiment with mixing in ground up weeds, or a little bit of carrot juice for a nice orange color... however, my tortoises (even the ones who NEVER eat cuttlefish bone!) heavily approved and helped themselves to these calcium cupcakes within minutes of placing them into each enclosure.

_Ppps: I am not the inventor of home-made calcium blocks. There are several conversation threads on the Tortoise Forum (e.g. HERE and HERE) that mention them long before I ever thought of making them. They don't however, mention the exact ratio of water and CaCO3 (Calcium Carbonate) that works best. _


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## biochemnerd808

I should follow up to say that for those of you who don't want to buy a 50lb bag (even though it is only $8 at the feed store), Amazon has some 1lb and 5lb bags of Calcium Carbonate.


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## lismar79

Thanks for this! I'm so excited to try it. Is this one ok?
http://www.amazon.com/dp/B0064GZPPO/?tag=exoticpetnetw-20


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## Maro2Bear

@lismar - yes, the product that you highlighted is foodgrade and will work just fine.


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## Jabuticaba

Great tutorial! Thank you! 


May
THBs: Darwin & Merlin
Aussies: Dax, Vegas, & Cricket
IG: @AUSSOMEAUSSIES


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## leigti

I will definitely try this. My tortoise will not touch cuttlebone.


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## Tyanna

leigti said:


> I will definitely try this. My tortoise will not touch cuttlebone.




Mine either! Mine are in the oven as we speak!


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## leigti

Maybe a stupid question but is there any worries about the tortoise eating too much of this?


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## Tyanna

Someone mentioned adding a package of the instant jello...is that safe?


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## biochemnerd808

leigti said:


> Maybe a stupid question but is there any worries about the tortoise eating too much of this?


A tortoise generally won't eat more calcium than it's body needs. Calcium overdoses are more likely to happen from excessive sprinkling onto a tortoise's food.


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## biochemnerd808

Tyanna said:


> Someone mentioned adding a package of the instant jello...is that safe?


Hmmmm. I don't like feeding my kids artificial flavoring, and definitely not to my tortoises. Although it's probably harmless, I would instead mix in some carrot juice (vitamin A and orange color, yay!) if you are aiming for coloring it. Or you could put some weeds in the blender with the water you are adding, and produce a nice green block.


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## Krabby

This sounds like a great idea! I am going to try this. Wish me luck, I am not very good in the kitchen.


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## Tyanna

No worries mine don't look too appetizing. It's a work in progress. Learn as you go


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## biochemnerd808

Hmmm. It looks like maybe you need to add a little more water to make the mixture smoother, then tap the baking pan a few times to make them pack down better, @Tyanna


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## Tyanna

biochemnerd808 said:


> Hmmm. It looks like maybe you need to add a little more water to make the mixture smoother, then tap the baking pan a few times to make them pack down better, @Tyanna




Yes I was definitely thinking more water! And maybe baking them a little longer too!


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## Taylor T.

I know this is food safe, but will it work for this?


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## biochemnerd808

Taylor T. said:


> I know this is food safe, but will it work for this?
> View attachment 98980



@Taylor T. - the chemical formula of pickling lime is completely different, it is Calcium Hydroxide Ca(OH)2 which is NOT safe for tortoise calcium source. The common name "lime" is unfortunately sometimes misleading. You need Calcium Carbonate (CaCO3) for this. Here is a link to a small bag of it on Amazon: http://www.amazon.com/dp/B00HFFD3O8/?tag=exoticpetnetw-20 - there are other listings on there, too.


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## Taylor T.

biochemnerd808 said:


> @Taylor T. - the chemical formula of pickling lime is completely different, it is Calcium Hydroxide Ca(OH)2 which is NOT safe for tortoise calcium source. The common name "lime" is unfortunately sometimes misleading. You need Calcium Carbonate (CaCO3) for this. Here is a link to a small bag of it on Amazon: http://www.amazon.com/Carbonate-Greenway-Biotech-Inc-Limestone/dp/B00HFFD3O8/ref=sr_1_3?ie=UTF8&qid=1412618742&sr=8-3&keywords=calcium carbonate - there are other listings on there, too.



Okay thanks I'll look at that.


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## Tyanna

Operation make my tortoise like to nibble on calcium: fail. 

Next cooking I'll have to add some carrot juice or weeds into the mix!


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## biochemnerd808

Tyanna said:


> Operation make my tortoise like to nibble on calcium: fail.
> 
> Next cooking I'll have to add some carrot juice or weeds into the mix!



Haha, that's too bad! He might just not need any right this moment - and then one day you'll walk by and half of the darn thing will have been eaten up.


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## Taylor T.

Is 0.05 to much Crystalline Silica?


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## biochemnerd808

@Taylor T. - is that 0.05g? or %? or mg?


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## Team Gomberg

Katie, would you ever consider selling these? I like them a lot (although my guy eats cuttlebone just fine) but I'm not up for making them..LOL
If you would consider selling/shipping batches, let me know


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## Cornwell1

Yeah. Same i would be up for buying some


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## Taylor T.

biochemnerd808 said:


> @Taylor T. - is that 0.05g? or %? or mg?


@biochemnerd808 It says that it is percent on the bag.


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## biochemnerd808

That is probably safe then. That is a VERY small portion - basically, silica is just small sand impurities.


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## leigti

Team Gomberg said:


> Katie, would you ever consider selling these? I like them a lot (although my guy eats cuttlebone just fine) but I'm not up for making them..LOL
> If you would consider selling/shipping batches, let me know


Me too! I'm not very good in the kitchen either.


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## Taylor T.

It says on the bag that it is calcium carbonate. Do you think it's tortoise safe, though? It was originally for making mortar, so I'm not sure.


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## Tyanna

I guess that's a good use for the calcium blocks if you aren't going to eat it, Taz..


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## Lindsay Chen

I know that this question is kind of off topic but do any of u have any recommendations on what to feed my Russian tortoise?


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## leigti

Lindsay Chen said:


> I know that this question is kind of off topic but do any of u have any recommendations on what to feed my Russian tortoise?


There is an endless list. Check out the Russian tortoise section and there are lots of suggestions there.


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## Lindsay Chen

Thank you!


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## biochemnerd808

Team Gomberg said:


> Katie, would you ever consider selling these? I like them a lot (although my guy eats cuttlebone just fine) but I'm not up for making them..LOL
> If you would consider selling/shipping batches, let me know



Haha, @Team Gomberg I honestly don't think I have the time to make and sell them at this point... between keeping up on filling Etsy orders, taking care of the tortoise clan, and not even mentioning the hubby and the kids... plus I would worry about them breaking during shipment. If someone else wants to take over this niche market, I totally don't mind.


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## Tyanna

biochemnerd808 said:


> Haha, @Team Gomberg I honestly don't think I have the time to make and sell them at this point... between keeping up on filling Etsy orders, taking care of the tortoise clan, and not even mentioning the hubby and the kids... plus I would worry about them breaking during shipment. If someone else wants to take over this niche market, I totally don't mind.



But yours have some type of magic in them to make them more tasty to tortoises! Mine still hasn't touched his. Touché, little tortoise.

I will keep working on making it more appetizing to him.


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## Randi

Going to look for sources of Calcium Carbonate here in Canada, and going to try it! My tortoise refuses cuttlebone and food with calcium sprinkled on it. I even tried a tortoise block. 

This gives me hope! Haha, thanks so much for the share!


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## sachin.ambhore

Guys..i m from india. N here we get tablets of calcium carbonate with vitamin D3. So instead of making calcium blocks can i jus leave those tablets in his enclosure , so tht he ll nibble on it? Pls advice


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## rabbidbros10

Good work


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## sachin.ambhore

Randi said:


> Going to look for sources of Calcium Carbonate here in Canada, and going to try it! My tortoise refuses cuttlebone and food with calcium sprinkled on it. I even tried a tortoise block.
> 
> This gives me hope! Haha, thanks so much for the share!


Hii


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## tortoiseowner101

I heard that when calcium carbonate is heated, it decomposes into calcium oxide.


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## Loohan

Great idea, but i would be leery of agricultural lime, let alone lime sold for masonry. I have heard some of it contains such toxins as cadmium.


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## HLogic

tortoiseowner101 said:


> I heard that when calcium carbonate is heated, it decomposes into calcium oxide.



It probably would be better, if using the calcium carbonate shown in the links, to use carbonated water (club soda) in the mixture. The ground limestone noted in the links contains a great deal of calcium oxide already. Calcium oxide + water yields calcium hydroxide (not good) but calcium hydroxide + carbon dioxide (from the club soda) yields calcium carbonate (good). I'm not certain it would make that much of a difference but the chemistry works...


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## Loohan

Of course it is not necessary to heat it.
I got a bunch of calcium carbonate on eBay. Since i only have 1 baby to feed, i just mixed a bit with a small amount of water to make a plaster, and rolled it into a tight ball. Put it on his dish, and it shrunk a bit as it dried.
He hasn't touched it though, and it's been several days.


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## Valentine's Mom

Dumb question, Is there a shelf life on the blocks? I would like to spend the day making them but don't want to throw them out in a month or two if Valentine doesn't like them at first.


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## JohnnyB65

Wow I don't know how I missed this. Thanks for the great tutorial.


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## Kristen and cirby

How often do you give your turtle these goodies. If I give Cirby a cuddle bone she eats it right up. I don't feel comfortable giving her one everyday and they are expensive.


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## Kent

Thanks for the information. I think I might try it.


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## Dessy

Hi i made a small sample for my tortoise to try and i had flukers calcum with d3 supplements laying around. My bars have started turning a little green, is this normal?


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## JohnnyB65

I bought all the stuff from Amazon including a silicone muffin pan to make up a batch, but my tortoise doesn’t touch the stuff. He pushes it around a little and it looks like he might have tasted it when I first put it out months ago.

I don’t know what else to do with it except toss it unless I can smash it up and mix it in his food maybe. I understand that too much is harmful.


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## Gillian M

biochemnerd808 said:


> Tortoises need *calcium* in order to build strong bones, a strong shell, and healthy organs. Ideally, they are fed a widely varied diet of nutritious weeds and dark leafy greens that have high levels of bio-available calcium in them. Adding a sprinkling of a healthy plant-based supplement such as TNT can help significantly. However, sometimes a tortoise's calcium requirements go beyond what is found in the plants we can provide.
> Some tortoise keepers rely on *sprinkling calcium powder* on tortoise food. However, this has the danger of causing a dosage beyond what a tortoise needs, and may actually cause health problems. For this reason, I like to provide healthy tortoises with calcium sources that they can help themselves to, as needed. Tortoises seem to have a good instinct about when their body needs more calcium.
> 
> Great idea! I've a strong feeling my Greek tort -Oli- needs calcium. He only eats Roman lettuce, tomatoes and recently carrots. NO food for torts here. I have NOT got the oven, and other things needed for the recipe. Is there an alternative?
> 
> Appreciate an answer, thank you.
> 
> 
> 
> 
> 
> *Cuttlefish bone* (found in the bird aisle of most pet stores, or available in bulk online) is a good option. However, not all tortoises seem to care for cuttlebone. *Quarry chalk* is a good source of calcium. It is widely available in the UK and some other countries, but is hard to come by here in the US. Finally, *man-made calcium blocks* are another good source of calcium. Some such products are available in the pet trade. However, I have found them to be _ridiculously expensive_, and they often have _undesirable ingredients_such as sugar or artificial dyes and flavors. For this reason, I did a little research, and decided to try making my own calcium blocks.
> 
> 
> 
> 
> _The home-made calcium blocks are tortoise-approved!
> _
> After seeing how ridiculously easy it is to make the home-made calcium blocks, I wanted to share the recipe and procedure with you, so that you and your tortoise(s) may benefit from it as well.
> 
> First, you need to decide on the calcium source. *Food-grade calcium carbonate*(CaCO3) is one good option, sometimes called Limestone flour. Another, more affordable and more easily available source is so called *Agricultural Lime* (CaCO3) - I got it at our local feed store for $8 for a 50lb bag! Agricultural lime is produced by pulverizing limestone or chalk, and is commonly used as a soil amendment. Please make sure to read the label CAREFULLY: you want to make sure that it not so-called hydrated lime, that it does not contain Magnesium Carbonate, and that it does not have any other ingredients and impurities in significant amounts. Here is the kind I bought:
> 
> 
> 
> 
> _One of many good options
> _
> The only other ingredient you will need to make lime blocks is water.
> For tools, you will need:
> 
> 
> a large mixing bowl
> a *sturdy* spoon to mix with
> and some kind of mold that will withstand 200 degrees F (93 degrees C). I used a silicone muffin pan that I got at Goodwill for $2
> an oven, pre-heated to 200 degrees F (93 degrees C)
> 
> It took a little bit of mixing and adding to find just the right consistency. Here is the ratio of ingredients that I found to work best:
> 
> 1.5 cups of warm water (H2O)
> 7 cups of CaCO3 powder (Ok, sue me; I used a liquid measuring cup to measure the dry powder, which I know is a no-no in cooking... but in this case it worked fine, since I was just aiming for keeping track of the ratio that worked)
> 
> 
> 
> 
> 
> First, I measured the Calcium Carbonate Powder into the mixing bowl. Then I made an indentation into the powder, and slowly poured the warm water into it. Then I very carefully stirred the mixture, to minimize clouds of powder flying up and all around. The mixture quickly gets very thick, so you really do need a sturdy spoon made of metal or wood. A spatula didn't cut it.
> 
> 
> 
> 
> _Yum! Calcium paste!
> _
> Keep on mixing until there is no more liquid on top, and no more pockets of powder at the bottom. It will get progressively tougher to mix, and will start looking like mortar or thick plaster of Paris.
> 
> Next, spoon the Calcium Carbonate + water mixture into the molds you have chosen. The amount I made was exactly the right amount to fill all 12 wells of the muffin pan, plus 1 small cup.
> 
> _*NOTE*: Please DO NOT dump excess slurry down your drain. It can clog your drain and/or wreck your in-sink disposal. I took the bowl outside and hosed it down. It is perfectly safe just to dump it onto your garden or your lawn.
> In fact, if you don't have a lot of tortoises, and don't want to have the remnants of a 50lb bag (minus 7 cups) of agricultural lime sitting in your garage... just spread the rest into your lawn, or dig it into your flower beds or raised garden beds!_
> 
> 
> 
> 
> 
> Next, carefully place the mold into the oven. I used a cookie sheet under the silicone muffin pan since it is a bit wobbly. Set the timer to 1 hour.
> 
> 
> 
> 
> 
> After 1 hour of baking, open the oven door and carefully pull the oven rack out far enough that you can safely touch the calcium cakes. You will notice that water has risen to the top of them. Use a paper towel or napkin to wick off the excess liquid. This will significantly cut down on the drying time.
> Bake for another 2-3 hours, depending on your oven. I checked every hour to remove more liquid, and after a total of 4 hours, they looked completely dry, and had shrunken in the molds.
> 
> Carefully remove the mold(s) from the oven, and place somewhere to cool down. This took a long time. I used our handy dandy infrared thermometer to check the temperature of the calcium blocks, and waited for them to almost be cool enough to touch.
> Once they are cool enough, carefully remove each calcium block from the mold, and place it on a cookie drying rack. They should come out easily. I let them sit like that overnight, just to make sure all the moisture had dried out.
> 
> 
> 
> 
> 
> The next day, I put one of these beautiful calcium cupcakes into each of the tortoise enclosures, and packed the extra ones into ziploc bags for later use. Within minutes of placing the cakes into the enclosures, the tortoises congregated around them, and took a few nibbles. Pretty soon, they were sporting cute little calcium mustaches...
> 
> 
> 
> 
> _Jill approves.
> _
> The part that really made my day: Amber, my XXL female Russian tortoise had just laid eggs. She has been stubbornly refusing to eat cuttlefish bone, and does not eat weeds if I have sprinkled them with calcium. However, by evening, her calcium cake looked like this:
> 
> 
> 
> 
> 
> I hope you have fun making your own calcium blocks, and that your tortoises enjoy them as much as mine do! Please keep in mind that in order to properly absorb calcium, a tortoise needs UVB to produce vitamin D3. You can read a little more about this HERE.
> 
> By the way, I copied this article from my tortoise blog, if you are interested in reading more.
> 
> Ps: When you mist your enclosures, please avoid spraying the calcium cakes too thoroughly (you might take them out briefly), because otherwise they may disintegrate.
> 
> Pps: You might experiment with mixing in ground up weeds, or a little bit of carrot juice for a nice orange color... however, my tortoises (even the ones who NEVER eat cuttlefish bone!) heavily approved and helped themselves to these calcium cupcakes within minutes of placing them into each enclosure.
> 
> _Ppps: I am not the inventor of home-made calcium blocks. There are several conversation threads on the Tortoise Forum (e.g. HERE and HERE) that mention them long before I ever thought of making them. They don't however, mention the exact ratio of water and CaCO3 (Calcium Carbonate) that works best. _


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## Gillian M

leigti said:


> I will definitely try this. My tortoise will not touch cuttlebone.


I wonder why. Torts seem to love it.


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## biochemnerd808

Valentine's Mom said:


> Dumb question, Is there a shelf life on the blocks? I would like to spend the day making them but don't want to throw them out in a month or two if Valentine doesn't like them at first.



There shouldn't be an expiration date. It's calcium carbonate with water, so nothing that would rot or go bad. Limestone sits in cliffs for millenia.


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## biochemnerd808

Kristen and cirby said:


> How often do you give your turtle these goodies. If I give Cirby a cuddle bone she eats it right up. I don't feel comfortable giving her one everyday and they are expensive.



I buy cuttlebone in bulk on Amazon, and then I put several throughout the outdoor enclosure, and 1 in each indoor enclosure. If your tortoise eats it readily, I would let it, it probably needs the calcium.

I just put a calciu. Block in each enclosure. The tortoise's help themselves as they need it.


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## biochemnerd808

Dessy said:


> Hi i made a small sample for my tortoise to try and i had flukers calcum with d3 supplements laying around. My bars have started turning a little green, is this normal?



You might have moss or algae growing on it... the big tortoises at our house eat them up before they have a chance to turn color, but in the baby tank, the block has a bit of a green hue, lol.


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## biochemnerd808

JohnnyB65 said:


> I bought all the stuff from Amazon including a silicone muffin pan to make up a batch, but my tortoise doesn’t touch the stuff. He pushes it around a little and it looks like he might have tasted it when I first put it out months ago.
> 
> I don’t know what else to do with it except toss it unless I can smash it up and mix it in his food maybe. I understand that too much is harmful.



If your tortoise won't touch it, you can grind it up and use it for sprinkling.


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## Aunt Caffy

biochemnerd808 said:


> Tortoises need *calcium* in order to build strong bones, a strong shell, and healthy organs. Ideally, they are fed a widely varied diet of nutritious weeds and dark leafy greens that have high levels of bio-available calcium in them. Adding a sprinkling of a healthy plant-based supplement such as TNT can help significantly. However, sometimes a tortoise's calcium requirements go beyond what is found in the plants we can provide.
> Some tortoise keepers rely on *sprinkling calcium powder* on tortoise food. However, this has the danger of causing a dosage beyond what a tortoise needs, and may actually cause health problems. For this reason, I like to provide healthy tortoises with calcium sources that they can help themselves to, as needed. Tortoises seem to have a good instinct about when their body needs more calcium.
> 
> 
> 
> 
> 
> *Cuttlefish bone* (found in the bird aisle of most pet stores, or available in bulk online) is a good option. However, not all tortoises seem to care for cuttlebone. *Quarry chalk* is a good source of calcium. It is widely available in the UK and some other countries, but is hard to come by here in the US. Finally, *man-made calcium blocks* are another good source of calcium. Some such products are available in the pet trade. However, I have found them to be _ridiculously expensive_, and they often have _undesirable ingredients_such as sugar or artificial dyes and flavors. For this reason, I did a little research, and decided to try making my own calcium blocks.
> 
> 
> 
> 
> _The home-made calcium blocks are tortoise-approved!
> _
> After seeing how ridiculously easy it is to make the home-made calcium blocks, I wanted to share the recipe and procedure with you, so that you and your tortoise(s) may benefit from it as well.
> 
> First, you need to decide on the calcium source. *Food-grade calcium carbonate*(CaCO3) is one good option, sometimes called Limestone flour. Another, more affordable and more easily available source is so called *Agricultural Lime* (CaCO3) - I got it at our local feed store for $8 for a 50lb bag! Agricultural lime is produced by pulverizing limestone or chalk, and is commonly used as a soil amendment. Please make sure to read the label CAREFULLY: you want to make sure that it not so-called hydrated lime, that it does not contain Magnesium Carbonate, and that it does not have any other ingredients and impurities in significant amounts. Here is the kind I bought:
> 
> 
> 
> 
> _One of many good options
> _
> The only other ingredient you will need to make lime blocks is water.
> For tools, you will need:
> 
> 
> a large mixing bowl
> a *sturdy* spoon to mix with
> and some kind of mold that will withstand 200 degrees F (93 degrees C). I used a silicone muffin pan that I got at Goodwill for $2
> an oven, pre-heated to 200 degrees F (93 degrees C)
> 
> It took a little bit of mixing and adding to find just the right consistency. Here is the ratio of ingredients that I found to work best:
> 
> 1.5 cups of warm water (H2O)
> 7 cups of CaCO3 powder (Ok, sue me; I used a liquid measuring cup to measure the dry powder, which I know is a no-no in cooking... but in this case it worked fine, since I was just aiming for keeping track of the ratio that worked)
> 
> 
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> First, I measured the Calcium Carbonate Powder into the mixing bowl. Then I made an indentation into the powder, and slowly poured the warm water into it. Then I very carefully stirred the mixture, to minimize clouds of powder flying up and all around. The mixture quickly gets very thick, so you really do need a sturdy spoon made of metal or wood. A spatula didn't cut it.
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> _Yum! Calcium paste!
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> Keep on mixing until there is no more liquid on top, and no more pockets of powder at the bottom. It will get progressively tougher to mix, and will start looking like mortar or thick plaster of Paris.
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> Next, spoon the Calcium Carbonate + water mixture into the molds you have chosen. The amount I made was exactly the right amount to fill all 12 wells of the muffin pan, plus 1 small cup.
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> _*NOTE*: Please DO NOT dump excess slurry down your drain. It can clog your drain and/or wreck your in-sink disposal. I took the bowl outside and hosed it down. It is perfectly safe just to dump it onto your garden or your lawn.
> In fact, if you don't have a lot of tortoises, and don't want to have the remnants of a 50lb bag (minus 7 cups) of agricultural lime sitting in your garage... just spread the rest into your lawn, or dig it into your flower beds or raised garden beds!_
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> Next, carefully place the mold into the oven. I used a cookie sheet under the silicone muffin pan since it is a bit wobbly. Set the timer to 1 hour.
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> After 1 hour of baking, open the oven door and carefully pull the oven rack out far enough that you can safely touch the calcium cakes. You will notice that water has risen to the top of them. Use a paper towel or napkin to wick off the excess liquid. This will significantly cut down on the drying time.
> Bake for another 2-3 hours, depending on your oven. I checked every hour to remove more liquid, and after a total of 4 hours, they looked completely dry, and had shrunken in the molds.
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> Carefully remove the mold(s) from the oven, and place somewhere to cool down. This took a long time. I used our handy dandy infrared thermometer to check the temperature of the calcium blocks, and waited for them to almost be cool enough to touch.
> Once they are cool enough, carefully remove each calcium block from the mold, and place it on a cookie drying rack. They should come out easily. I let them sit like that overnight, just to make sure all the moisture had dried out.
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> The next day, I put one of these beautiful calcium cupcakes into each of the tortoise enclosures, and packed the extra ones into ziploc bags for later use. Within minutes of placing the cakes into the enclosures, the tortoises congregated around them, and took a few nibbles. Pretty soon, they were sporting cute little calcium mustaches...
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> _Jill approves.
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> The part that really made my day: Amber, my XXL female Russian tortoise had just laid eggs. She has been stubbornly refusing to eat cuttlefish bone, and does not eat weeds if I have sprinkled them with calcium. However, by evening, her calcium cake looked like this:
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> I hope you have fun making your own calcium blocks, and that your tortoises enjoy them as much as mine do! Please keep in mind that in order to properly absorb calcium, a tortoise needs UVB to produce vitamin D3. You can read a little more about this HERE.
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> By the way, I copied this article from my tortoise blog, if you are interested in reading more.
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> Ps: When you mist your enclosures, please avoid spraying the calcium cakes too thoroughly (you might take them out briefly), because otherwise they may disintegrate.
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> Pps: You might experiment with mixing in ground up weeds, or a little bit of carrot juice for a nice orange color... however, my tortoises (even the ones who NEVER eat cuttlefish bone!) heavily approved and helped themselves to these calcium cupcakes within minutes of placing them into each enclosure.
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> _Ppps: I am not the inventor of home-made calcium blocks. There are several conversation threads on the Tortoise Forum (e.g. HERE and HERE) that mention them long before I ever thought of making them. They don't however, mention the exact ratio of water and CaCO3 (Calcium Carbonate) that works best. _


I just made a batch myself using club soda as was suggested in this thread. Turned out nice and stark white.


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