+2 I run an 80 watt in my 300It will help but it doesn't get rid of the Ich. For it to fully work you would need all of the Ich to past through it, and in a tank with things like rocks and such it's very hard for that to happen. It does also help with the overall health of a tank, so it's not a bad thing to add. As for size, watts, you need to check the spec of the unit.