I was using a fluval 404. Worked fine for a couple months, but would have to be cleaned constantly seemed like after a couple days the water flow would slow down, and I'd rinse the pads again, and after about 6 months the motor melted completly. Having it the same level also let air get into it. Better if you can get a smaller model that might sit lower than the water level. Mine was only slightly lower. I had to bump the pond height up to 6" above the ground and started running fluval Fx5s that have a pump at the bottom. I can't speak for other's expiriences on here, but that's mine. I ran one of the Fx5s on my 75 to get the bio started, and it kept that tank sparkling, and the monsterous waterflow didn't really effect my fish lol.