Caribsea aragonite reef sand 15lb 68kg caribsea aragamax aragonite reef sand sea floor special grade is a calcium rich aragonite marine substrate packed with beneficial bacteriasea floor special grade is ideal for deep beds plenum systems reef or fish tank bottom coverapprox 1 2m diametercaribsea aragonite helps to create a natural biological and mineralogical balance to discourage nuisance algae growth and promote healthy fish and invertebratescontrols nitrate nitrite ammonia and ot