In a pretty bad mood after just losing half my Cardinal tetra and maybe more to come. I know they are very sensitive to any changes in water parameters and a more maturely established tank is preferred. That being said over 48 hours they had acclimated very well to the tank. Then, yesterday, I gave them some hikari tubifex worms in a freeze dried cube. As soon worms were coming lose, I pulled the cube out. Probably removed 90% of the worms. Didn't realize how many were compacted in there! Still though, a feeding frenzy ensued. It was a cute thing to watch the tetras go after them. However I knew this was over feeding as some had to have stuffed themselves with at least 4 worms plus. The next day (today) I come home from work to see several are dead while others are struggling to swim upright, tipping to their side or upside down with expanded abdomens. Meanwhile my Rams are doing wonderfully and colors are starting to come in. They did not participate in the worm frenzy as they were still unfamiliar with the tank. I check parameters with API every 8-10 hours religiously. 0-0- 5 to 10 nitrates. I haven't had the heart to research anything yet but I thought I'd start by sharing my experience here.