At what size does CC become sand?

[Nate C]

I gather from lurking on this and other forums that crushed coral = bad & DSB = good.

What if you have something in-between? I found some teeny tiny crused argonite "sand" that has grain sizes around 1.5mm. Is this size small enough to create a beneficial nitrate-reducing environment?

Thanks in advance.

 

[Atari]

Any substrate will work.. they only differ in the maintenance they require.

I have a 2" bed of the same aragonite you're talking about and get good NNR.

 

[indy]

Nitrate reduction comes from the depth of the sandbed, not the size of the sand its growing in. NNR comes from anaerobic bacteria, so the dsb needs to be deep enough for it to grow. CC is advised against because it allows big chunks of detritus to work its way down where it can't be eaten by detrivores and then rot. Small sand keeps it up at the surface where snails, crabs, etc can get to it.