One of my goldfish (Neptune) seems to be spending most of the time on the bottom of the tank with belly touching the gravel, looking ill, back fin down, long tail drooping then he will perk up again and begin swimming normally, (usually when I walk by the end of the tank from which I feed them, which is both fishes normal habit) I have noticed that when he does start swimming Neptune keeps coming to the top of the tank for air. I have an airstone and pump and have also added a slow release oxygen tablet to increase the amount in the tank to see if this helps and have fed only peas today. My other fish appears to be fine.
I have been away for 4 days, the fish were fed but the house was empty and the weather has been cold. Could the drop in temperature have something to do with it? I changed the water 2 days before I went. Today I have tested the water ph, ammonia levels are fine but our water is very hard and the hardness seems to have risen? Will reducing the hardness help and how do I do it?
thanks Frances