Pumice in canister filter?

[Moozillion]

Anybody use broken up pumice instead of those ceramic rings in a canister filter?

 

[cdmay]

Yes! I collect pumice that washes up on my beach at work. It’s weird because the pieces look like rounded stones, but they float. The pumice that washes up in Palm Beach originates down in the Caribbean and is light grey or whitish.
Anyway, I walk the beach after storms and collect the smaller pieces and after rinsing use them in one of the canister filter trays. Seems to work very well.
BTW, as the pumice floats you typically find it way up the beach with the lightest of the beach flotsam.

 

[Moozillion]

Yes! I collect pumice that washes up on my beach at work. It’s weird because the pieces look like rounded stones, but they float. The pumice that washes up in Palm Beach originates down in the Caribbean and is light grey or whitish.
Anyway, I walk the beach after storms and collect the smaller pieces and after rinsing use them in one of the canister filter trays. Seems to work very well.
BTW, as the pumice floats you typically find it way up the beach with the lightest of the beach flotsam.

WOW!!!!
Picking up floating volcanic rocks at the beach is simultaneously weird and cool!!!!

 

[mark1]

I use it , it works better than space , it does work , and it's cheap in large quantities , almost anything will work the difference is how well ... good ceramic bio rings will have a lot more surface area per same volume , like 10x the area ...... I would guess in a small area like a canister filter ceramic rings are as good as you can do ........ bio-balls , matala , plastic pot scrubbers or body scrubbers all have more surface area than pumice rocks per same volume ........... at least it's what I think .....

 

[Yvonne G]

I buy those imitation Scotch Brite pads at the dollar store and cut them to size.

 

[Markw84]

Pumice is an excellent choice for a canister filter. It has about the highest surface are for nitrifying bacteria of any media choice. Much more than pads, and even some pumice can have more than the ceramic rings. A good type of pumice will have a lot of internal surface area where they bacteria is much more resistant to drying or washing off when cleaning the filter, so can be a good choice above bio-balls, especially for canisters.

Its just that not all pumice is the same. Different durability, porosity, and even different chemistry of the material it is made of. so you need to be sure you get a type of pumice that has the porosity you need and does not leach chemicals that can affect your water chemistry and ph.

 

[mark1]

Mark , could you reference something I could read on the surface area of pumice per cubic foot ..... in keeping fish I was told different , I am under the impression it was the least of anything mentioned , I do use it to fill space , if I thought it was a good media i'd like that ....

 

[mark1]

I've never seen evidence other than anecdotal as to the efficacy of pumace , looked into it a bit tonight , as i'm always looking to improve filtration ...... after reading some research on the use of pumace vs ceramics , I did underestimate pumice , I feel better about using it , next spring i'll break it up and maybe add some more , it's a bit expensive to fill a 55gallon drum with ceramics here's one comparison study , between poraver/expanded glass(ceramics) , sand , limestone , basalt and pumice ......

http://studyres.com/doc/14958246/the-importance-of-surface-properties-in-the-selection-of-...?page=3

Results
The results obtained for the porosity of the particulate
materials are presented in Table 1. Contact angles with the
various liquids employed and surface tensions compo-
nents of the nitrifying bacteria studied are summarised in
Table 2 and Table 3, respectively. It can be seen that both
bacteria are hydrophilic. Nitrobacter is intrinsically the most hydrophilic.



Table 4 shows the data of the interfacial free energy of
adhesion between nitrifying bacteria and support materi-
als, immersed in water. The lowest values were obtained
for limestone-Nitrosomonas and limestone-Nitrobacter ,
followed by the values for the interaction of the nitrifiers
with basalt.The surface charge of the supports was measured as
electrophoretic mobility. Figure 1 shows the average values
of the determinations. In the pH range 6±9 all the mate-
rials are negatively charged, except limestone that shows a
positive charge for pH values under 6.7. Basalt and poraver
have similar surface charges in the pH range studied.
Pumice is the most electronegative followed by sand .
All over the experiments, due to the medium buffering
capacity, the value of pH was in the range of 7.2±7.8, which
is well within the optimal range for the nitrifiers. The
results of nitrification in the airlift reactors are shown in
Fig. 2. Poraver and limestone are the supports that showed
greater efficiency. In the case of poraver it took 4 days for
all the ammonia to be oxidized to nitrite, and all nitrite was
oxidized to nitrate after 10 days. With limestone, both
oxidations occurred in 2 and 12 days, respectively. Sand
and pumice are the materials in which nitrification is
slower. Basalt shows an intermediate behavior.

The adhesion of the nitrifying consortium to the different
types of carriers seems to be strongly affected by the
electrical charges of the interacting surfaces. Both types of
bacteria present negative surface charges and they adhere
preferentially to the supports that show higher surface
charges. This explains the lower efficiencies obtained with
sand and pumice, which are the most negatively charged
particles


Moreover, in the case of limestone, carbonate ions can
affect the pH, since the protons released during the first
step of nitrification can be neutralised by them, inhibiting
a pronounced decrease in pH.
Besides, it is also possible that in the presence of
limestone a higher concentration of inorganic carbon
might be available for the metabolism of the autotrophic
consortium. The good efÆciency displayed by poraver,
although not in good agreement with the thermodynamic
approach, can be explained by some calcium bridging but
mainly by its high surface area on account of its high
porosity. The mechanical resistance of poraver is relatively
low and this may lead to some disintegration of the par-
ticles with a consequent increase in surface area. However,
if disintegration occurs to a large extent this may lead to
the reactor wash-out.
Pumice has also a very high porosity, but when
grounded to small particles do not acquire a round shape.
By microscopic observation it is perfectly seen that they
are very irregular and sharp. This type of shape increases
the erosion phenomena and promotes a higher detach-
ment of cells.
5
Conclusions
The surface properties of the materials have a great
influence on the adhesion phenomenon. Materials having
low surface free energies of interaction with bacteria
favour the formation of more stable biofilms. The surface
charge is also determinant for the bacterial attachment. As
a consequence the basalt and limestone showed very high
efficiencies. The porosity is also relevant for a good
colonization of the carriers as was proved by poraver.
Sand showed low efficiency and a great difficulty in
fluidization.
Irregular particle shapes, like in the case of pumice,
promote a strong abrasion and erosion of the biofilm.
Although poraver had a good performance, its low
mechanical resistance can be detrimental when working
with a great concentration of particles and high fluidizing
velocities



Bacterial strain support

Nitrosomonas
Sand
23.20
Nitrosomonas
Limestone
9.74
Nitrosomonas
Basalt
12.76
Nitrosomonas
Pumice
31.41
Nitrosomonas
Poraver
43.53
Nitrobacter
Sand
31.33
Nitrobacter
Limestone
11.67
Nitrobacter
Basalt
18.15
Nitrobacter
Pumice
43.05
Nitrobacter
Poraver
58.73



Table 1.
Porosity of support materials
Support
Porosity (%)
Sand
29
Limestone
11
Basalt
15
Pumice
48
Poraver
79

 

[Markw84]

Mark , could you reference something I could read on the surface area of pumice per cubic foot ..... in keeping fish I was told different , I am under the impression it was the least of anything mentioned , I do use it to fill space , if I thought it was a good media i'd like that ....

sorry Mark, but you beat me to the google search. Although over the years I've looked at a lot of effectiveness comparisons, to give you a link to a current study would have been a google search for me too. Glad you found something that satisfied your question.

 

[mark1]

thanks Mark , it was a search to find much more than folks who sold pumice to tell you it was great ...... once I found one though , there were quite a few , that one being the simplest ........ i'm always looking for better and cheaper ways to filter my turtles water.......I was impressed with myself keeping 3 4" wood turtles in a homedepot cement mixing tub since may without ever changing the water , their still out there , temperature is a bit tough in such a small amount of water , but the water is in great condition , I will say most of their filter is filled with pumice , I guess it was a good choice as a filler , I figured it had to be better than gravel ......... when I think about filtering water , I often think about your pond , the pond is impressive , I think the filtration has to be more so ..... i'd guess you don't have a choice but to be good at it ........ a problem with one of my ponds is at worst a day or two's work to redo the whole thing , a problem with your pond would be nothing short of a disaster , I couldn't imagine ......

 

[cdmay]

I use it , it works better than space , it does work , and it's cheap in large quantities , almost anything will work the difference is how well ... good ceramic bio rings will have a lot more surface area per same volume , like 10x the area ...... I would guess in a small area like a canister filter ceramic rings are as good as you can do ........ bio-balls , matala , plastic pot scrubbers or body scrubbers all have more surface area than pumice rocks per same volume ........... at least it's what I think .....

You may be right Mark, I haven’t done a lot of research. The pumice I collect does work better than the plastic bio-balls I’ve used though.
Ceramic rings and ‘noodles’ seem to be effective too and they can be cleaned and reused.

Other things I’ve experimented with are micron filter pads, bags of resins (or whatever it is), filter bags filled with various carbon mixes and numerous grades of other filter pads. Everything works to a certain degree but then the issue becomes, for how long? Micron pads become clogged PDQ and although carbons are awesome for water polishing and removing odors, they too become rather useless after a short time.
As I’ve mentioned before, keeping small aquatic turtles is like maintaining very large tropical fish with a large bioload of waste. So imitating what large fish keepers do is a good idea.

 

[cdmay]

Pumice is an excellent choice for a canister filter. It has about the highest surface are for nitrifying bacteria of any media choice. Much more than pads, and even some pumice can have more than the ceramic rings. A good type of pumice will have a lot of internal surface area where they bacteria is much more resistant to drying or washing off when cleaning the filter, so can be a good choice above bio-balls, especially for canisters.

Its just that not all pumice is the same. Different durability, porosity, and even different chemistry of the material it is made of. so you need to be sure you get a type of pumice that has the porosity you need and does not leach chemicals that can affect your water chemistry and ph.

Your first comments are pretty much what I had always thought regarding pumice as a filtration medium.
What I had NOT considered though was there are different grades of pumice...although it makes sense that there must be.
The stuff I find on the beach is incredibly lightweight and is porous through and through.

 

[ZEROPILOT]

Has anyone had issues with pumice breaking down and causing damage to impeller assemblies and the like in cannister filters?
I've had a lot of damage from silt in the past. But no experience with pumice.