[markam87]

4 of my 5 fishes have suddenly died this morning almost at the same time. I took some water to petsmart and all the water levels were out of range, but it's probably been like this for a while, I doubt this would be the cause for the sudden death of the fishes. I had one otocinclus catfish, one red wag platy and 3 zebra danio. Only the red wag is alive. Last Wednesday someone gave me a used but still working heater, and the water has been at about 79 F since. He also gave me some decorations that I rinsed and put in the aquarium. I just changed about 75% of the water, added some ph increaser, ammonia remover and water conditioner, and some salt. What should I do? Thanks!

 

[tankman12]

How long has the tank been setup? Is it cycled?
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[markam87]

I've had it set up for almost a year, and although I've lost a couple of fishes before, I could see it coming, or I had a fungus outbreak. This time it was a shock, the fishes were fine before I went to bed, swimming and eating. I change about 10% of water once a week. Thanks for your response.

 

[tankman12]

Well the oto probably died from starvation. The zebras prefer colder water but will do fine in warmer water. Maybe it is all those chemicals going into the tank. The ph increaser is not very good on fish. What ammonia remover? The salt, only the platy likes. A 75% wc is pretty big, if you dont know how to do it properly. Did you make sure the temp was the same? What is the ammonia, nitrite, and nitrate readings?
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[Flint]

You need to discontinue the use of the salt, pH increaser and ammonia remover. What ammonia remover are you using? Seachem Prime is a water conditioner that detoxifies ammonia and nitrites and that's all you should be adding to your tank unless you are medicating. You also need to be doing much larger water changes, at least 50%, matching the temperature of the new water to the temperature of the water in your tank as best as possible. Just add your 20 drops of Prime after you take the water out and add your new water back in. The fact that your levels were "out of range" tells me your tank is not cycled so I suggest getting an API Master Liquid Test Kit, some Tetra Safe Start and doing a water change whenever you see that ammonia and nitrite hit a combined number of 1ppm.