Aquarium Water Pumps & Water Movement: Marineland Maxi-Jet PRO
I have a 37 and got the 600 model in the link above and set it up as a water circulating pump. I found it was too much for my LPS
(and sand for that matter) and had to really reposition some rockwork to deflect a lot of flow. If I had to do it over, I definitely would have gotten the 400. If I needed more, I could have simply added another 400. Two smalls beats one big in case you loose one, and it offers more flexibility for placement, etc.