01-24-2009, 12:15 PM
Join Date: May 2006
| | Re: Common causes for death or illness of fish
Diana, thank you for writing such an informative article backed by scientific study citations.
The linking of MB (mycobacteriosis) to fish stress reminded me of an observation that I have had over the years on neon tetra-only tanks. One day a neon tetra didn't look healthy while the rest were ok. I let that fish remained in the tank until finally s/he gave up, usually weeks or months later. Then another fish became ill within days. But when I immediately moved a sick fish to another tank, a second fish became sick within days while others remained healthy. When I moved that second fish, a third one became sick not long afterward. Unless the sick fish was getting very weak, s/he liked to stay within a group.
I had observed the above phenomenon several times. It could be mere coincidence. But it appeared that something was causing one fish sick at a time. Sometimes I saw neon tetras (typically only two) engaging in a head-to-head fight. A fight could be so nasty that it lasted up to 20 seconds, despite other neon tetras trying unsuccessfully to break up the fight. It looked as if some strong personalities were not willing to back down and therefore decided to fight it out. I wonder whether the one-sick-at-a-time phenomenon was an indication of dominant fish(es) taking it out on an easy target. When that easy target was gone, another one became the target. Being a target stressed the fish and therefore came down with disease. But then it could be someone trying unsuccessfully to dominate the population, engaged in too many fights, and therefore being stressed out.
Another subjective observation, but on fish de-stressing. Sometimes, typically couple hours before the tank light went off at night, all the neon tetras in a tank spontaneously aligned themselves loosely in a procession and leisurely paraded down the length of the tank. Upon reaching one side of the tank, everyone turned around, with the leaders became the followers, and paraded to the other side of the tank. It was as if they were doing some kind of bonding ritual - taking turn to lead and follow. Very soothing to watch. That went on for sometime before the 'parade' broke off.