You should visit your local pet store, in the aquarium fish section, and check out the products available for maintaining the health and well-being of your fish.

And you should also learn the generic drug names or IUPAC chemical names for the commonly prescribed antibiotics.

I'm not saying those two suggestions are in any way related, other than the possibility that doing both could save you a great deal of money, in certain situations. Otherwise, grocery stores and big-box stores with embedded pharmacies often sell generic antibiotics at prices below your drug co-pay, but you would still need a prescription, and therefore an office visit co-pay. It pays to shop around.