What Now?

[Biulu]

I keep 5 goldfish and 2 recently started getting balance problems. So, I thought it must be the swimbladder and gave them some peas. This worked, however I need to give them now almost a pea a day to make them more or less swim properly. So, I wonder whether it is something else that is affecting their swimbladder?

I feed them spirulina flakes, pellets and tetramin flakes, alternating these regularly. Their water is clean with an oversized filter, furthermore the tank has crypts, anubias and java fern (all plants they do not really like to eat). The temperature is set at 20 degrees.

Any advice is welcome! Thanks, Eleonore

 

[Aquanaught]

I'd be quarantining them from the other fish for starters
Just incase