My tank is so screwed up, I don't understand. It's a 37 gallon, completely cycled (no ammonia or nitrite ever) and so heavily planted that nitrate stays under 5 even if I miss a water change or two (not that I do that often). I also drip-acclimate the fish for at least an hour before adding them. But all the fish I get die!!! Well, except for a few, which makes it even weirder. I have this one endler that is so small that I forgot I even had it, a platy that never comes out if the cave it hides in but manages to stay healthy, and the entire school of glowlight danios that I bought originally. These I have had since I started the tank 8 months ago, and they are quite healthy...even though I have never seen any of them eat! Literally never. I have no idea what they live off of, but all of these particular fish never go up to the surface when it's feeding time. BUT, all the other fish it have tried to add have died. Over the course of the tank's history, I have attempted to add 3 platies, 11 guppies, 2 endlers' and 8 mollies (not all at once though obviously). The longest one has lasted is 2 months; most only last 2 weeks. Well one thing's for sure, I'm not buying live bearing fish EVER AGAIN. The fact that I've bought 26 and only two were healthy enough to survive speaks volumes (and I assume they are just genetically weak since my water is consistently pristine). Since the glowlight danios have been going strong and not a single one has died in 8 months, maybe fish from the cyprinidae family are the way to go? What would you in my situation? Do you think zebra danios, tiger barbs, white cloud minnows, or some other hardy cyprinid schooler is what I should try next? Oh and I buy all my fish from a LFS renowned for it's quality, not petsmart or petco.