Is it better than any HOB filter like the AC 110, emp 400, penguin 350, etc? Is it also highly recommended to use for a 40 gallon and to use it with an emp. 400? Thanks.
A 305 and an emp 400 would be fine for a 40g. I run a 305 and an ac110 on my 55g and it works just fine. However, I think the 305 is overpriced and there are better filters that you could get for a better price. Eheim 2217 is a good example.