Hi everyone,
So the past week or so, I've been losing my oranda goldfish one by one. My tank is 70 gallons. I keep it at 74F (23C).
About 1.5 to 2 weeks ago, I noticed a spike in nitrates (I think from overfeeding - my bad). So I did a large water change and kept testing the water every other day to keep it around 20ppm or less.
I had 4 orandas in the tank around 3 inches. I noticed one developed a white slimy looking growth on his body and had what i believe was anchor worm so I took him out for meds and QT for a week. He got better and looked fine but a day later he died. At this point I had treated the whole tank for anchor worm too. Yesterday, I noticed two of my other orandas breathing fast and not being active. This morning I found them both dead, one was floating upside down and the other laying on the substrate. I currently still have one in the tank, who's still swimming around but seems spooked when I come near the tank
I don't have any pictures unfortunately. Anyone any ideas what happened? Is there some disease in the tank that would require me to bleach the system and start all over?