Do you have any cycled filter media in any other tanks? If so you could cut some of that out of a cycled filter and pop into your new filter, then it will be cycled already. No, just moving gravel over wont cycle it, because the gravel has all the stuff stored in it if you move it all the stuff in the gravel will just move.
You'll have to cycle the tank if you dont have cycled media, which could take upto 6 weeks.
Sand is alot better to use in betta tanks as its easier to clean. I use it in my tank, and when you get dirt on top of it you can get a thin airline tube and suck it up with that.
If you dont know how to cycle a tank then read up on it on the internet. How is your betta?
Do you have a breeding trap to put him in? You could also just make your own sort of breeding net, by getting a thin plastic tub thats been used to store peaches when bought or something like that etc lol , put a few tiny holes in it each side.
Also yes, they do get affected by nitrates etc, all fish do. Can you buy yourself a test kit? If your cycling a tank this is essential, because you need to read test results to find out if and when is cyced.
