I had a similar case sometime ago, happen two times, most of the fish mysteriously died, all on the same day too, a sunday. Thought it was the water company doing some UFO tampering of the water lol found out that they do nothing special to the water and that the same amount of chloramines added has been the same for many years. I did experiments after to see if I could figure out what could have went wrong. Most times people just say ammonia may have done it, not possible if it was 0 and also from my hands on research, fish rarely if ever die from ammonia, a fish will die if it's weak to begin with. I have put tanks under controlled tests with seriously off the charts ammonia and never lost one fish, even small ones, no negative side effects either, fish are generally pretty strong, just depends on the fish. For my situation, my conclusion was perhaps it was because I didn't dechlorinate for the entire tank instead just the amount I put in from the tap and maybe the chlorine did them in. Now I do for entire tank and have never lost a fish yet. I would say most of the time it must be something not right with the water or maybe even mixing conditioners or if you put your hands in the tank and they have something on them that messed up the water. Whatever the Xfile reasons, best thing is to just ride it out, don't beat yourself up about it and get back on the seahorse. Fish die, go out and buy a new one. i try not to treat my fish like pets, in nature they are just fish in the water and they die out there too. I would think if you invested that kind of money then you should be quite the advanced fish keeper if not then you were in over your head. I only spend based on my knowledge and experience. I never buy a fish that I haven't done lots of research on and even then I always gets stumped by things I didn't find in the research. Just curious how long have you been in the hobby ?
