Nitrates, the end result of food and poo,not a good thing for a reef tank, bio balls,cannister filters,filter pads,crushed coral,live rock ,detrius,surplus food and frozen food that is nor rinsed with ro/di water all contribute to escalating levels. A filter sock well placed and washed every 3 to 4 days will catch more muck than you can imagine, regular water changes, a good protein skimmer, proper flow and good house keeping will contribute to lowering nitrate levels, now a tip for test kits, if you have algae problems and your test readings are low, guess what! there not, the algae is consuming the nitrates and only the surplus is showing, its just like testing for ammonia, you should never see it but its being produced constantly and consumed by.I dont mean to be longwinded but I Hate Trates lol.Steve |