So I have been battling high nitrates for a couple weeks. I have had multiple water changes, cut way back on my feeding, fixed the skimmer problem, and still have the nitrate problem. When discussing this again with my LFS he is thinking that since my tank had been set up for a long time with a Grouper, and a couple of eels my nitrates were probably super high to start with. Since I didn't change the sand, he seems to be thinking that no matter how many water changes I do until i get rid of the source of my problem it isn't going to do me any good. He seems to think there may be tons of "crap" from the previous inhabitants of my tank that needs to be gotten rid of. He is suggesting some sort of filter that will allow me to stir up my sand and such in huge amounts of water that will clean my water. Thoughts?