I'm quite confused with the whole gph thing for my 29g. The 29g was given to me as a gift and I was told that they had an 800gph and a 400gph power head in a tank that kept sps and softies. I would like to have a reef tank and recently finished my cycle. My water is great, everything checks out and I purchased a hydor koroli 850 thinking it would be sufficient. this thing looks to be a bit powerful for medium flow. I have it at the top pointing upwards for water agitation now and it has slowed the flow a bit in the rest of the tank however, it still seems a bit powerful. before I had it placed lower in the tank and it was making a somewhat hurricane effect in one spot of the sand bed. My dad got me a clown since my water was finally good to go. The clown loves to swim right where the powerhead is and get launched upward... does the 850 seem to be a bit powerful for my future reef set up or should i swap out for something a little less powerful?