I found an information that one of the successful Sulawesi cardinal shrimp keepers used reverse flow UGF in his tank. Well known Vietnamese breeder used regular UGF, the same way as in Caridina tanks.

From my uneducated in this area point of view this makes sense: they have to have very small water changes and be not disturbed at all, and pushing up everything from the small gravel or large sand and collecting it from the water column in the canister filter should help with keeping water clean. Cleaning canister filter will not disturb shrimp in the tank.

What should be the size of the substrate, not allowing shrimps to fall through and not restricting flow much? Some layers, large and smaller kind of substrate?

Someone mentioned that water from canister filter is low in oxygen, and, if direct it to the bottom of the tank (not to the spray bar at the top), this is not good. What could be done about it?

Anything else that I should know?