I used to have aquarium fish, but I practically don't remember anything. I can say for sure that the Internet has all the information you need, which will be enough for you to figure it out.

I also never got aquarium fish. I'm not very interested in this, to be honest. I prefer animals that you can pet and play with. I can throw you this article https://pawfectpawprint.com/how-to-use-melafix-for-betta-fish/. Read it and see other articles in the fish section. I think this is what you're looking for.

If I'm not mistaken, it still depends on the breed of fish and size..

Good afternoon! Well, I also wondered this question, but when I bought a fish, I just found a good article about gold nugget pleco and read a lot of useful things thanks to which I properly care for aquariums and know that my fish live in comfort. Therefore, a lot of things need to be read on this site.