Crushed stone is generally limestone or dolomite that has been crushed and graded by screens to certain size classes..
Crushed stone is the bases of biological filtration, as it creats perfect environment for nitrifyinh bacteria. What allowed undergravel filters to be shunned was the widespread use of live rock. The biological filter with the largest amount of surface area is the best, as it provides more area for nitrifying bacteria colonization.
Highly porous, this limestone material makes an excellent habitat for aerobic bacteria
.It is this anaerobic bacteria that converts the nitrate to free nitrogen, and it is released to the atmosphere. Now the nitrogen cycle is really complete, and the goal of biological filtration is fulfilled. |
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