this tank has been up for 9 plus years,and after a little neglect the nitrates got a little high,so I hit it with 3 back to back 30 gal. water changes and all is good.I don't think I'm going to add much more livestock..it has a adult 9in. hippo tang,adult true percula,a baby true percula (clown's)..just added a few newbies and all is well so far..