Hello, everyone. We had seven little goldfish in our 40-gallon aquarium. One died Sunday. We tested the water, did a 30% water change (as the PH was high), and thought we'd be okay. Then our favorite little fish was dead on Monday morning. Heartbroken, we changed 50% of the water and the PH and ammonia levels seemed okay. The next day, our biggest and oldest fish died. In desperation, we put the four remaining fish in a small holding tank, and completely cleaned the big tank, including the gravel and plants. We filled it, and added drops to the new water to cycle it. We know the water is supposed to sit for at least 48 hours before we put our fish back in, but in the middle of the night, one of the fish was looking very listless, and we didn't think he'd make it until morning. We were worried that the old water they were sitting in was poisoning them. So we put the fish in the big tank with the new water, and hoped they'd survive the night. As of this morning, all were still alive. The ammonia level is about .35, the PH level is about 7.9-8.0. (We are getting nitrate and nitite tests later today.) Were we crazy to put the fish in their big tank so quickly?

Has anyone else had something similar happen?

(We've had these fish for years. They were abandoned in a little outdoor pond at our last house, we cared for them for several years in their pond, and we took them with us when we moved. Could the move from outdoor to indoor cause such awful mortality rates? We are sick with grief.)


Thank you for listening. Any advice would be greatly appreciated.

The only time I heard of that happening was on a community water supply that had put a super dose of chlorine in the system.

I'll check into that. Thank you.
(Do you know if there is a way I can test for chlorine in my tap water? I'm very new to all this.)

Ammonia is more toxic at a higher pH, so your reading of .35 at a pH of 8.0 is stressful at best. It's not enough to kill them all off rapidly, but who knows, it may have been higher than that previously (or even after) you tested. My guess would be that you have a significant nitrite reading. I have seen more deaths from nitrites than from ammonia, for one because nitrites aren't easily reduced by water changes, and for two because most people don't regularly check for them. Add 1.5 tablespoons salt for every 5 gal to keep your fish from uptaking the nitrites and get your nitrites checked ASAP. Even if nitrites aren't the problem, the salt won't hurt. "What kind of salt?" you ask? Good question. Pure sodium chloride - this can be "aquarium salt", solar salt, rock salt, water softening salt, canning salt, even table salt... just check the label to be sure it doesn't contain any anti-caking additives (iodine is okay).

I never "age" my water before adding it to my tanks. I have far too many tanks and far too many gallons for it to be practical, but honestly I wouldn't bother with it if I only had one 10 gal. Whether you do it or not is up to you, and in some instances (such as if you are on well water), it may be beneficial, but in most instances adding the dechlor and putting the water directly into the tank isn't going to harm anything.

It's not a good idea to add all the fish at once in an unestablished tank, not to mention that 7 goldies in 40 gallons is at least 3 too many. I am sorry for your loss, especially the loss of your "favorite". I know what that's like and it can be incredibly disheartening. The good news, if there is any, is that you're down to the proper number of goldfish for the 40 gallons you have to work with, and should they all pull through, they'll be able to live comfortably in it for the rest of their fishy lives. It sounds like your problem is water quality, and that is also good news - it could be a lot worse.

Best of luck.

You can buy test kits similar to the ones you get for ammonia, etc. Don't bother worrying about the chlorine content until or unless you can rule out nitrites.