yellow cucumber

[Mike]

Sand sifting cucumbers... we kept a smaller one in our 20g for a while, but eventually it cleaned out the sand bed and started starving and getting smaller. I moved it to the big tank and it has been doing fine ever since. So one would probably starve in your small tank. Plus you would have to worry about it nuking your tank if it gets too stressed or dies. They can release a toxin, which in an aquarium can be fatal to itself and all other occupants. We have had one or two in the big tank for years with no problem though.

A sand sifting starfish would quickly starve in that small of a tank.

How about a small sand sifting goby? It would keep your sand clean. What other fish do you have? Or how about some nassarius snails?