I have an aquarium that has had no fish in it for twenty days. I had an ich outbreak which killed all my fish. I'm getting a new betta tomorrow and was planning on putting him in my three gallon fluval that has no ich. But the tank that has been fishless for twenty days is five gallons and heavily planted. It's the tank I plan on moving him too once I know for sure all the ich is gone. The other tank is only three gallons. But would it be fine just to put him in the five gallon? Is twenty days without a fish host long enough to kill off all the ich?