50% is actually bi monthly.... every 2 weeks... my bad..
Its not gill flukes.. had them, this is different
As far as chlorine or chloratamine, this started 2 days before my scheduled water change. The previous water change had been done over 2 weeks before that... and i use prime.. so it cant be
as said in the initial post, all params are normal. and water change was just done. This is a well established tank, it cant be ammonia.. plus it read 0pmm
The only other thing i can possibly think is internal parasites. I went through callamanus worms about 2 months ago, but i eradicated them. No one else is showing symptoms. The fish cant be over 2 years old, so its not age
-Just another day in paradise-