It's a rather planted aquarium, i have a cluster of floating elodea and a sword fern plant, along with a large piece of driftwood where they could hide under. What has happened so far: One tetra died at the beginning (within 5 hours of purchase), which I can only imagine being credited to stress. Another two have died from, what I assume, a whiteish line band towards the middle of the fish going vertically, it was like a disease where one fish had it, died, and it probably spread to the second, by which time I had quarantined it just to witness it die. The aquarium store thinks that it's a fungus infection, which I can only attribute to stress as well, considering how the ammonia and nitrate tests both came out to be 0ppm...The other three fish seem to be fine except for one (which has a red/exposed gill and breathes really quickly, but I've read that this is a possible genetic defect for tetras), and there is no sign of this whiteish growth on any of them. Is it crucial that I keep them in a school of 6+ or can they survive for the time being in a group of 3?
From this data, I would tend to think the fish had some problem. By any chance have any in the store tank also died or shown this? I would not buy from this tank if yes.
It is always possible that fish can be damaged during netting; I am extremely careful, to the point of taking considerable time when I have to net fish, but even so I have once or twice managed to injure a fish. The stress of being chased and netted and moved only adds to the problem, as you correctly mentioned.
But, there is also the problem that the fish might be carrying something. Neon tetra are very weak fish these days, due in part to many years of commercial inbreeding.
As to the numbers, with all tetra which are characins, the more the better, long-term. However, having only three is not going to kill them off, but it would be advisable to try and narrow down the issue before acquiring more. As I said, if these symptoms are in the fish store tank, forget them.
Byron.
