fish dieing in a tropical tank ?

[lisa_s21]

i have a 20gallon tank 1 of my fish had mouth rot so i put in some medicine for mouth rot then the next day all the fish were at the top so i done a water change on the tank , 1 had died another 1 is nearly dead all the rest r still at the top i have checked all the water there is nothing wrong with the nitrite amonia ,nitrate and ph the temperature is fine what can be wrong with them all i have done a couple more water changes as well can any one help ? i dont want them all to die , thank u
yes i did get rid of the clorine in the water when i done a water change i will put some more oxygen in the water see if that helps thanks
i have just put an air stone in the tank , the tank has been set up for about 5 years , there is 2 corries , 5 harlquines , and 6 platties so not to many

 

[A. Guy]

You should have moved them to a medical tank, then treated them, then you might've been able to stop the epidemic.
Treatment-Treat with anti-fungal remedy, you did the water change, so start to feed your fish food high in vitamin c.

 

[Firiun]

Maybe the chemical was for non-tropical fish. Buy a new fishtank to make the fish not have to be flushed into the porcelin gates.

 

[Momma Keesh]

What Chris said.
How long have you had the tank?
How many fishes do you have? Have you checked that you are not overstocked? What type of fishes do you have?
Maybe you are doing too many water changes. If all the chemicals are balanced then you may just need to step back and let things settle. Too many disruption, ie. water changes, can add to stressing the fish out.
It does sound like an oxygen issue though.

 

[Chris W]

did you condition the water after the changes as in remove the chlorine too much chlorine in the water will also kill the fish it could also be that there is not enough oxygen in the tank for them so their at the top gasping for air or 1 other fatal thing would be that they have swim bladder disease not able to swim hope this helps u out and good luck