Hi everyone. My partner and I have had a fluval edge for a number of years however, after a hiatus, we are only on our second round of fish. We set up the tank about 3 weeks ago, left it fish free for about a week whilst letting the supplied additives do their thing. We then added 2 moss halls and 2 bunches of weeds. At the same time we purchased a loach and a comet. After leaving them for a week, we then went out and purchased 5 small mix danios and 2 large silver danios. Pets at home seemed to have no issue with this so we thought happy days and went about enjoying watching our fish. Then yesterday, we noticed our comet was becoming very lethargic, parking itself on the weeds in the back corner with its back fin down. We thought it was trying to avoid the danios but, having watched it this morning, im worried its on its way to fishy heaven. Having read posts on here, im now worried that a) our water quality is iffy but I haven't had a chance to test it and b) our tank is horribly overcrowded. We thought coldwater would be the easiest option for relative newbees, although obviously not! We would be extremely grateful for any assistance you can offer as I really don't want my comet to die...its one of the family thanks again.