as other post stated i am setting up a new tank. have lots of crushed coral from my african tanks can i mix it with the sand or will this just become a nitrate trap.
More than likely the crushed coral will end up on the top and the sand at the bottom(sand filling in the space between the crushed coral eventually moving to the bottom). Defeating the purpose for why many use sand, other than the fact that crushed coral is a nitrate trap.. most critters benefit from sand rather than crushed coral.
Small amount for jawfish and burrowing gobies such as engineering gobies are good. Some gobies and jaw fish actually pick them up to build their burrow.
I build DSB with the lowest layer using crushed corals and I screen it off though so the deep burrowing animals cannot disturb the sand bed.
I build removable DSB pail with the lowest layer using curshed coral and they don't end up surfacing on top of the sand. However, in an open dispaly tank the story could be different.
My first question to you would be, did you ever treat your cichlid tank with any chemicals (copper specifically)? If you did, then you wouldn't want to use that crushed coral in a reef tank. Second, it can become a ntirate trap.