Random fish deaths?

I have a 20 gallon tropical community tank with, among other things, 5 threadfin rainbowfish and 6 cory cats (3 c. similis, 3 c. aeneus). Yesterday I did a routine water change, just like I do every week. I also checked my water params. Everything was fine--ammonia and nitrite were both 0.





Today, I woke up to find one of my c. similis and one of my male threadfin rainbows were dead. The cory had been worrying me for a bit, because it seemed lethargic, although it had absolutely no other symptoms that I could see. The rainbow was fine--he was displaying and chasing the other males when I went to bed.





Any idea what could have caused the deaths? I'm baffled. The cory may have been ill, but the rainbowfish seemed perfectly healthy.

Random fish deaths?
Have you been conditioning your water during changes? Maybe there is a high mineral or chlorine content in your tap water? This may make your fish 'lethargic'. Remember that if you have city water, at different times they add different things to the water. Fluoride, chlorine, etc... Maybe they added something new that your fish don't tolerate. If this sounds like something that may be of concern I suggest conditioning your water with water conditioner from your local pet store.





Happy Fish Keeping!
Reply:I am so sorry this happened. I don't know what could have caused everything so suddenly....maybe the rainbowfish was at the beginning stages of being ill, yet didn't look it? Maybe his immunity was changing at the time when you last examined the rainbow fish? Was the rainbow fish eating normally. Usually if they are eating, they are okay.





If you had checked the water params, and all seemed normal.... the only explanation could be a weakened immune system from your other fish.





:(
Reply:For a start your tank is too small.





Secondly if you mix males with females and there isnt enough places for the females to hide from the males then they will be harrassed to death.





And if some off your fish are lethargic, well wouldnt you be if you had been chased round the block for 24 hours!
Reply:your tank may for one be too small, or you under or over feed them. remember if you see a fish UPSIDE DOWN he is DEAD


if you see a fish ON HIS SIDE he is CONSTIPATED, so don't throw them out. when a fish eats too much he gets constipated, and his stomach and bowels get filled up and blocked with food, so the air in his stomach goes to the side, and he floats at the top on his side, practically unable to swim.ALWAYS CHECK BEFORE FLUSHING DOWN THE TOILET


ut also fish are the worst animals for life expectancy's, many fish die for just absolutely no reason what so ever, and their really is no cause for alarm. JUST REMEMBER TO GET THAT BODY OUT IF ITS UPSIDE DOWN the dead body may make the other fish sick and die, for they can release gases once dead, that are poisonous, e.g: Carbon Dioxide CO2
Reply:sorry about your fish. maybe it was just sick or old or stressed. well i dont think your tanks too small or that the fish arent compatible
Reply:Well if you aren't feeding your fish around the same time everyday they will eat at each other. Your fish could also not like each other, like some fish will eat at others if they're in the same tank together. You may not be giving them enough food. Your fish may also be alot older than you think and has been around for a while.


Hope it helps!!
Reply:What about Ick........ do you think they might have gotten cold????
Reply:among other things? what are they and how many? did you add water at the right temp and properly treat it before adding? How old are your fish? i know these are kind of basic but that is usually the best place to start.
Reply:Sorry to hear that.





The only time you really lose fish is after a water change so you really have to be careful and it sounds like you are.





You may have changed to much water (no ore than 20-25%)


the shock of too much new water can kill them.





The tempeture could have been off. water 2 degrees colder will kill fish no problem when its rushed into the existing water.





More times than not though you accidentally did something to kill your beneficial bacteria and you had an ammonia spike that killed the sensitive fish (cories are scaless making them really sensitive).





measuring parameters won't uncover it as it could time for the ammonia spike to happen and the bacteria recovered for the most part 12-20 hours later.





If you think that was it add a little bit of seachem stability evertime you clean the filter (1 capful) to avoid this.





you may have done something in the tank cleaning to stir up alot of ammonia if you didn't clean the filter.





Or the water conditioner you used somehow failed you.





hope that helps





good luck

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