Could anyone enlighten me please.
My stepson has a small (about 6 gallon) freshwater tropical tank, containing assorted barbs, one corydoras and a rapidly growing plecostomus. My worry is that the fish have always seemed to be struggling for breath. They show no other obvious symptoms, and don't seem to be particularly in distress. We have had problems with the filters clogging with decaying plant material and I added a second internal filter a while back, which resulted in both of them clogging in the outlet side and nearly causing a wipeout while we were away last week. Fortunately our friend who was feeding them noticed and changed some water. When I returned on saturday, I put the fish in a bucket of tank water, cleaned the sand which had turned black (in the tank water) then let it settle and syphoned out the muck. Refilled the tank using the bucketful of old tankwater that the fish were in, and fresh water with Aquasafe or similar. The fish were ecstatic, loved the clean tank and water and were breathing at a rate I considered normal. Its now 4 days on and 3 of the Pentazona barbs have snuffed it, and the others are fine, but breathing fast again. OK the deaths could have been from either damage caused by the near wipeout, or perhaps an ammonia or nitrate spike as a result of the drastic cleaning, but why the rapid breathing? The tank isn't overstocked, I added an external power filter at the weekend as extra precaution against the filtration problems and the water now is belting around and I'm sure they are getting the oxygen now that perhaps they lacked before. Could it simply be the temperature too warm. We have a glass thermometer, and it shows towards the top of the "green" zone, which I always assumed was OK. Could gill flukes or some other parasite cause the sympton, they dont seem to flick themseves any more than any other fishes. I'm stumped.
Thanks in advance, Bikenut