Ich problems
Hey Hey Im new to the hobby and I found myself in the same boat as you, luckily, this forum will help you out. I actually have a 21 gallon aswell, and I removed the charcoal in my filter and went out and bought an ich medication called "Nox-ich" whhich also said to treat for three days. WRONG!!! lol First off, if you have any scaleless fish in your tank, like tetras, you have to be careful because the ich medications will kill them (I know from experience). Secondly, I would listen to the pros on this forum, which will be responding to your post soon, stop with the store medication and go with the salt cure. You're supposed to raise the temperature to 85F, and add 1-3 teaspoons of salt (table salt is fine apparently) for every gallon. The raised temp will speed up the ich parasites life cycle, and the reason to treat two weeks is because the dreaded ich parasite has three stages; one where its burrowed into ur fish and gorging itself, onw where it settles to the bottom(full) and has a lil protective case and starts multiplying, and then when it releases into the water, lookin for another host-the final stage is the only stage in which the ich parasites are vulnerable to the salt, and thats why u want to treat for two weeks, to make sure you have killed all the parasites. This is what I have learned from this forum because my new tank was devastaed by ich, and I dont want it to happen to anyone else lol! The experienced people on this forum will give you exact instructions, and you may want to give them more info on your tank-like the other fish occupants, the curent temp, how you cycled ect. Good luck!!!And I hope you're swordtail recovers (theyre so cute!!)