Previously I didn't know about cycling so a lot of my other fishes died. I've been reading more in cycling lately and I just wanted to know if things are going right. I have a 15 gallon tank with 1 balloon molly in there for cycling. I read online that it's 1 fish per 10 gallons during cycling. Can I put any more? Also, when I was cleaning out my tank for this cycling process I washed it under cold tap water. Is something going to be wrong with the cycling process?

If you know some things about cycling, feel free to teach me too ^^
how often do filters need replacing? can you just wash it and use it over again? I have an aqueon 15 gallon started kit.