i wouldnt suggest feeding it frozen fish - and anything... should sort of thaw it out that way it doesnt freeze its internal organ..this is jsut my opinion. im sure many just dump it in like you... Ive used to do that but after i thought about it seems like its best to thaw it a bit
As said before, try prazi and then add salt. 3lbs per 100 gallon of water. DO NOT MESS WITH YOUR WATER, YOUR PH IS FINE. DO NOT MESS WITH IT OR YOU SCREW YOUR FISH UP SOME MORE.