I've had my 40 gal tank running for years. I now only have one goldfish in it and a small plec. A month ago I noticed red marks on the fishes body and red streaks on his tail. I tested the water and the nitrate had shot up to 80ppm. I did an immediate water change and continued to do so every day and added a Nitrazorb pouch. It took a good two weeks to come down where it sits now at 2.5. I just can't seem to get that zero! I've added Melafix for his tail and its a little shredded but even though he's 90% better (body is back to normal colour) now and again I catch him bouncing off the sides and even jumping out of the water hitting the lid. He's obviously distressed but apart from the ever so slight Nitrate, I don't know why?
I have a built in filter but was recommended to put in a pond pump for more aeration. The waters are Ammonia 0 Nitrite 0 pH 7
Hi! I’m not quite sure about the water levels, but my fish kept head butting the sides of the tank and it turned out he was trying to attack his refelection! We had to put stick on scenery around the back of the tank and he has since stopped doing it. He occasionally has the odd splash of his tail but otherwise he has calmed down! Just a thought, I hope this helps! X