I have inherited 9 goldfish in my new home. Initially, they were all healthy in November and ate pellets once or twice a month ( because winter) but in late February the water turned black and I never saw the fish. This is when I being a naive pond owner, cleaned the entire pond, and unknowingly scrubbed all the good bacterias. I feel like a murderer now as in the last 2 months 1 fish has died and all fish have been sick. We added pure aqua bomb 5 weeks back, tested the water and all looks fine but the fish health is no better. This includes a visit from Des Harris ( Southeast Koi club). He provided us Praziquantel for Flukes for the 1st week and FMG for the second dose. I see at least 4 of my fish have got fungal (the fish did had the same along with bruises during spawning). So now I have added API salt in 3 parts i.e 1kg every 8 hours. In total 3 kg for 300 liters of water because I noticed few had fungus and swim bladder symptoms. I have tested the water using api drip kit( PH 7.5-8, NItrite-0, Ammonnia- 0.25, Phosphate - 0.25)
Please advice what should I do further?