Do you use straight tap water for your goldfish What are your ph, gh levels. I tryed keeping fancy goldfish in the past but failed, African cichlids are fine . Think my water may be to hard for fancies , My Gh is around 20, ph 8.2
I use aged tap water currently treated with API stress coat and using pothos to lower nitrate. My tap water is GH 400+, PH 8-8.4, Nitrate 50+ I find that the harder the better.
