DEEP Aquarium substrate ideas?

[Moozillion]

I've never kept a tank with deep substrate- by that I mean 3-6 inches deep. My current thoughts for the new 75 gallon tank are: 2 inches of gravel; then another 3 inches of a sand cap. The idea being that all that substrate provides surface area for lots of organisms to clean the water.
I had originally tried to use an under gravel filter for the turtle who will be living in it, (a razor back musk) but he loves nothing more than to DIG!! And the minute he dug down to the plates of the under gravel filter, he interfered with its efficiency. This way, he can dig the sand to his heart's content, and it won't interfere with the efficiency of the organisms.
Thoughts?
Prior experience?
Thanks bunches!!!

Mooz

 

[ZEROPILOT]

So. No more undergravel filter?
Or are you still using one?
All of that sand above the gravel might have some flow issues. And might have some "dead" areas in the filter bed. I'd also be thinking about fine sand getting into the gravel layer and blocking the flow. But those are just theories.
I've never had turtles in an aquarium. Only large fish that loved to dig up all of the gravel.
I used reverse flow under gravel filters with gravel. Then got rid of the undergravel filters in favor of outside cannister filters. And eventually ended up with bare glass tanks. No gravel, sand or anything else.
It can be very aggravating

 

[mark1]

often i've used black(coarse)filter media mat over the under gravel plate with gravel on it ... the sand will work it's way to bottom , probably clog the substrate also.... i never really worried about efficiency , i'd pull so much water through , they always worked well enough .....

 

[Moozillion]

So. No more undergravel filter?
Or are you still using one?
All of that sand above the gravel might have some flow issues. And might have some "dead" areas in the filter bed. I'd also be thinking about fine sand getting into the gravel layer and blocking the flow. But those are just theories.
I've never had turtles in an aquarium. Only large fish that loved to dig up all of the gravel.
I used reverse flow under gravel filters with gravel. Then got rid of the undergravel filters in favor of outside cannister filters. And eventually ended up with bare glass tanks. No gravel, sand or anything else.
It can be very aggravating

Not using the under gravel filter for 2 reasons: 1) Nelson digs and uncovers the plates so he defeats the under gravel process and 2) the filter I got has no connection between the 2 plates! I would need 2 lift tubes and couldn’t figure out how to do that without 2 filters, so I got annoyed and just used canister filter without using the under gravel part.
I’d like to move him off gravel and onto sand.