phosphate in coral skeletons?

[glassbox-design]

Originally Posted by omard

And in fact, pores in rock become clogged up over time

...which can create anaerobic pockets for denitrifying bacteria, not necessarily a bad thing

Crushed coral has the possibility of leaching minute amounts of po4, if nutrient levels in the tank are low enough to enduce it. Most will have higher po4 levels that what is in the rock causing a build up of po4 in sand, crushed coral, and live rock and will not experience any leaching.

Any natural source has the potential to leach po4, but your LR would be a much larger source than CC, IMO. I wouldn't worry about it... As Amcarrig said, the problem of CC is the trapping of detritus and uneaten food.

[missionsix66]

Originally Posted by amcarrig

People generally recommend not using crushed coral because it's easier for detritus and uneaten food to get stuck in it and it can cause elevated nitrates if not kept clean.

This was what I was trying to point out.

[conjuay]

Well, that's good to know...
The 'cup'coral skeleton seems to be an excellent hair algae grower, the best (Worst) algae grower in the tank.
Thanks everyone!