DEADFISH

no one really ever told me... 1 molly(Female) 1catfishand then in a coupple days 15 fry (mollies)
and ihave a ten gallon tank

Boxermom

50% once a week is normal for a cycled tank. However, you have an uncycled tank with health problems so I would recommend 50% every day until it cycles and you complete treatment.

BTW, its really kind of a pain to have to respond to 200390432 different threads about the same type of thing. I would be easier, and less confusing both for you and for us, if you could stick them all in the same thread.

Isabella

When your tank is cycled and mature, with all the fish you want in, it depends on the number of fish. The more the fish, the more the wastes. And that means more water changes. If you get a test for nitrate, you'll know how many and how large water changes you need. You should always strive to keep nitrate at 0, and if you can't, just keep it as low as possible. Most of people here I'd say perform between 10-30% weekly water changes, some perform larger and more frequent water changes than that. It really depends on the number of fish and the kinds of fish you have.

There are some people that have densely planted tanks (with special lighting and substrates) with very few fish. Because healthy plants are able to filter the water themselves, and because small and few fish produce little waste, these people perform very little and very rare water changes.