I used to use only Whispers when I did FW and liked them a lot. Now that I am all salt I still use the smaller number two on 2 of my 20's and my little 15 Gal tnak and they have worked just fine. In FW I had the 4's-3's and even a 5 turbo (did not like the 5 tho). On a bigger tank I think they have many drawbacks tho and for my other tanks I use only Emperors for the last few years and I love those filters, the ease of pad replacement is the best part of them, plus they turn a lot of water. Now many here will say you need this and that and they are not wrong either but as I always say I believe simple is better.