both of those powerheads shoot out a thin jet of water,but don't really move alot of water.you can modify the maxijet if your handy-check the diy threads or the seios move lots of water.with a 35gal tank an 820 seio will work wonders,but if you have a sand bed maybe the 620 might be a better choice.there are also some people who will make and sell the majijet mod for a reasonable price-just check the diy threads.