What happened to my fish?

[lauralogic]

Having a problem with my two veiltails.

10 gallon, water fine- a little too much algae (they really like it).
Water parameters were absolutely fine and fish were healthy last night.
This morning I woke up to a half empty tank. My hang on filter had overflowed through the back and was dripping on my floor. I put some new water/ph additive in the tank and went to work. When i came home and saw the fish they were fine. I took a nap and woke up and they were gasping on the bottom of the tank.
I did an almost 75% water change, and no help. One is sort of zigzagging and swimming on its back. I t was heartbreaking, but I decided to move them to a quarantine tank with a bubble disk and clean water.

They arent doing so well, but i figured, if the water is toxic, better to have them in clean water to die.

Anyone know what happened here? Im at a total loss and heartbroken. Anything I can do that wont stress them out any more? (theyve been moved alot today)

Thanks.

[AngelMom]

Welcome to the forum. So sorry to hear about your fish.

You haven't filled out your profile so it's a little hard to completely answer your question. When you say that the water parameters are fine, we don't know what that means. Do you just check pH and temp, or do you also check for ammonia, nitrItes, and nitrAtes? Do you check for hardness (GH and/or KH) as well?

There is no doubt that the poor things have been stressed out. It is possible that if the water you added was at a different temperature than that in the tank that they had problems dealing with the change in temperature.

Also, the large change in water may have contributed. More than a 30% change should never be done. You started with about a 50% change due to the accident, so another 75% on top of that means that only about 30% of the original water remains.

Did you use a decholrinator when you refilled the tank and did the change? If not, they may have been reacting to the chlorine in your water source (assuming it is chlorinated).

When fish swim upside down, it is usually due to a problem with their swim bladder. Sudden temerature changes are one factor that can bring on a swim bladder disorder.

If you haven't already done so, you can try to add some Stress Coat. It may help.

Good Luck!