treating a tank that had mysterious sick fish
I have a low-tech tank that was doing well until I added some fish from my trusted LFS- yes, I quarantined them, but apparently not long enough.
Anyhow, I added a school of six microrasboras, and within one week of adding them, they died, and took all my ember tetras with them. it was apparently ich, as my housesitter said they all looked like they had salt on their fins. However, I was out of town and she had directions to feed and do lights only, as she isn't a fish person. There are galaxy rasboras, white cloud minnows and cherry shrimp left in the tank, all apparently healthy.
My question is this: since I didnt have photos of sick fish, and I dont have their tiny bodies, I dont really know what happened in there. I am wondering if and how to treat the tank, and is there a way to determine if the parasite or fungus is still present in the system without putting new fish in there to test?