I've got a 200l tank and I'm currently trying to deal with a (at the moment) minor case of ich. I'm trying to get my tank up to 31⁰C as I've been told this helps but even with two 200w heaters turned right up I'm only at 30⁰C. The room temperature eight now is 17⁰C. Should 2 200w heaters be enough or should I get 2 300w heaters?