Disappearing pleck - ill goldfish

Question
Dear Lee,

A few months ago my 2 goldfish died of something undetermined. The only symptoms were them lying on their sides at the bottom of the tank with arched backs.

At the time I had a plek and so after they died I was advised to do a maximum water change but not complete so that my plek would not be too distressed.

This I did, along with buying pH and nitrate/nitrite test kits which I now use regularly.

However, I bought 2 new fish and one died the other day unexpectedly and without symptoms.

I again did an also complete water change, but discovered that my plek appears to have completely vanished from my tank! Do you have any ideas?

My other fish is now ill though with the same symptoms as my first 2 fish. I have tested the pH and nitrates and they seem fine. I use water conditioner for new water and also use the cycle aquarium bacterial stuff.

Do you have ideas? It's quite warm in the tank but I have been told that goldfish don't mind if it's quite warm.

Do you have any ideas as I'm at a loss about what is causing the illness and what has happened to my plek!

Thanks in advance.

Vanessa

Answer
Goldfish do much better in cooler water, they just don't care for warmer water. Try adding aquarium salt to your tank, I have found this has worked well for listless goldfish when I was in the pet industry. With warmer water there is less oxygen in the tank for them also. For your current fish, I would add a few ice cubes to drop the water temprature slowly for them and add some aquarium salt. You should notice an improvement in their behavior with the cooler water. Ideally, I wouldn't keep goldfish in water over 70 F.
As far as your pleco... he may have jumped out of the tank at some point as they do not just disappear, or he passed away and the remains decayed to where you do not see him.
Happy fish keeping!!