Massive Ammonia spike

[nfras]

On my small coldwater tank (8 gal, maybe smaller) I got a massive ammonia spike.

Water change on Friday, 50%. Afterwards pH 6.8, ammonia <0.1ppm
Saturday pH 6.0 ammonia >>10ppm
It's already killed one of my fish.

The only thing I can think of that I did differently was to feed the fish with dried blood worms rather than flake. Could this be the cause?

[kimmers318]

I doubt the bloodworms were the only cause....it probably has more to do with too high of a bioload. How many, what type and size are the fish in the tank? Since you said you already lost one, I have to guess there is more than 1, and have a feeling you may just have too much in a small tank. As juveniles they have a much smaller bioload, but as your fish grow to max size, obviously their waste amounts will grow with them. Feeding dried bloodworms in my experience is a waste of time...none of my fish will touch them (maybe the frozen has them spoiled?!), but I think it would take time for the bloodworms to begin to decay and become ammonia.
Another thought...did you check your tap water? This is hoping that I am wrong and your stocking is good :)....I have heard of people finding sudden amounts of ammonia or nitrates in their tap water for some reason usually pertaining to a malfunction at the treatment plant.

[f1oored]

I'm going to assume that your small tank was cycled properly and you have been having success keeping your ammonia levels down until now. If the only thing you have changed is the food, it is possible that it was responsible for the spike. I've read in other places that high protein foods will cause higher ammonia levels both when uneaten and after digestion. I also believe that the 10ppm ammonia is what is making the water more acidic.

I would do a water change (50% or better) every few days until you get your ammonia down and your ph closer to neutral. Stop with the bloodworms also. Remember on such a small tank it is real easy to screw things up. A pinch of uneaten food can toss your whole system out of wack.

Testing the water from the tap is also a good idea. You said you tested after the water change and everything was alright so my guess is that your tap is fine and it was the bloodworms that caused the spike.

[nfras]

Ammonia was also high last night so did another 50% water change.
Tap Water is pH 7 and no ammonia. I treat it with a dechlorinator which would also remove any trace ammonia.
Also, the fish has survived. He's not looking too hot but still swimming.
The tank is set up with three 3 inch goldfish. I usually feed them with flake but got some bloodworms for my tropicals and gave the goldfish a treat too.
My own feeling is that the bloodworms didn't go down too well and that they created the ammonia spike. The problem being that it will continue to be a source of ammonia for a fair amount of time.
Thanks for the responses.