Help! Entire tank of Goldfish covered in white coating overnight.

[bdevol]

I am waiting for a pond to be installed. I am housing the fish Over winter. I have a number of fish Ill and need to understand what is going on. I don’t want to have this happen when they are moved. Any advice?

Last Thursday I discovered 3 or my shubunkin goldfish covered in fuzz. Gills red with labored breathing at the bottom of their 100 gallon tank. It happened suddenly over night. They had looked fine the night before. There was .25ppm ammonia. No nitrites or nitrates. Temp at 70. The ph was 6.5. When I took them out to get a closer look it seemed like the fuzz came off in the net. Putting them back the fuzz was gone and it appeared later that the extra fuzz had been shed in the tank. I did a 100% water change and everything seemed better. The fish were swimming but, no appetite.


I have 180 gallon tank with 7 baby shubunkins. Only an inch long. They received a water change and showed no signs of illness. Yesterday one died out of the blue. No signs of illness. Today I checked on the and another one had died. Now every fish I have is covered in the same fuzz and looks like all of them are struggling. I have a dojo loach with them an his side has the same type of fuzz

I Checked the water in the tank all water parameters are at zero, temp 65, ph 6.4.


I'm at a loss trying to understand what is going on and why so suddenly. I use prime and stress coat.

my tap water does not register anything but a low pH of 6.

I see Melifix and Pimafix recommend from a number of of websites. I am hesitant to go that route unless it’s the only option or the forum recommended it. I have seen just as many websites cautioning against it. I attached pictures. Can anyone tell me what’s causing this and how to treat and prevent this.

[Autumnsky]

Maybe Costia...? Ichthyology Symptoms are cloudy milky skin. I do not know about it personally. Others comment a treatment of Proform-C.
Costia information from the Fish Helpline