Fish came out of winter and have white film, 2 of them are starting to ulcer and have algae growing from the growths so SAP is the suspect. Filtration has been back up and running about 4 weeks. It's 10 fish averaging about 12 inches in 16k gallon. Ph 8.4, never read ammonia or nitrite because the pond is in full sun and stays some level of green anyway but nitrites are present in source water. Air on both bottom drains, another air pump on moving beds, 1 large and one small waterfall so good amount of aeration. 2 5500 gpm pumps on skimmer and waterfall circuits, 8500 gph on bottom drains to seive to moving beds circuit
2 to 3 weeks ago I dosed with formalin/malachite green and again a few days later. No change in the fish. Yesterday I treated the pond with pp trying to keep it at 1 ppm. Used sensafe test strips to monitor the levels. Tried to keep it at that level for 8 hours then reversed with sodium percarbonate. Intent was to clean things up as good as possible and hopefully knock down culprits to let the next formalin and malachite green treatment have the best effect possible.
How long before I can dose again with the formalin/malachite green after the pp treatment? This is horrible timing. We have sold the home, close and leave the end of this week and I feel horrible about this. I've left voluminous instructions for care of the pond and fish for the new owners but leaving this problem feels awful.
I've already packed my quarantine tank and extra air pump away to take to our new home. My best bet at this point is another full pond dosing of the formalin and malachite green. I don't have much time left. Some part of me thinks it might be better to cull the two that are showing signs of ulcers if I can't be sure they're recovering before I have to go and turn it over to the new owner 😭