Everyone really should read that sticky about ray safe medications.
I make it easy for myself. I bought bulk metrondiazole, nitrofurazone, praziquantel, and diflubenzurone. from nationalfishpharm.com. Cheap, pure.
Metrondiazole- treats internal infections, bacterial and protozoan plus some parasites
nitrofurazone- treats disc rot, and any external bacterial or fungal infections (love this med!)
praziquantel treats for internal parasites (also known as prazipro but WAY cheaper here)
Diflubenzurone treats fish lice and anchor worms
These are all ray safe and will treat nearly every infection or infestation your rays can get. I've never had something that one of these 4 won't fix. I've seen rays with nasty disc rot and cotton fungus make miracle recoveries with nitrofurazone. This is my #1 ray medication for fungus and bacterial issues. It's totally safe for them and doesn't crash your bio. Just dissolve completely in warm water first. For internal infections or parasites that Praziquantel can't clear up I like metrondazole and epsom salts dissolved in water then food (pellets) soak and fed to treat internally.
If you've invested 4 or 5 figures into your stock like a lot of us, you really should keep all 4 of these meds on hand 247 especially if you are getting new stock in and out of your systems or feeding live foods.