I am almost positive Apollo has internal parasites. How do I treat them? Should I treat the other fish in the tank too? And how do you get the parasites out of the tank?
Seachem's Metrodinazole- if fish are eating follow direction for meaking medicated food and feed it, and nothing else, twice/day for next 10 days. If fish not eating, dose the water according to the directions. It is a relatively benign med and hard to overdose
For angelfish with internal parasites, I treat daily with 35mg/gallon metronidazole, with daily 50% water changes. Metro is sold as Hex-A-Mit, and Flagyl. I turn up the temp to around 90-92F, this gets their metabolism going, and eating sooner. I treat the water for 10 days, withholding food the first 2 days. On the third day, I sprinkle a little metro on frozen brine shrimp, enough to make it look like a powdered donut. I feed the shrimp with metro once a day.
I'm sure guppies can handle temps in the low 80's, I would treat only the sick fish, there's no need to medicate well fish.
Internal parasites are something many fish live with normally in their digestive tract, it's similar to the bacteria in a human's digestive system. The problem is when they get out of control, more than the fish's natural immune response can handle. Many times some sort of stress can get it started.