Good evening this is my first day and post..purchased a lawnmower blemy last thur added to tank to help with algae,..after a few minutes he began rock work on algea...also was eating when I fed other fish...fast forward to this morning walked in and he had died..checked water and nitrate was 40 however all other fish were fine clown,red saddleback and niger trigger...could he have already been damaged..he was moving around great prior to this morning...