in my BC29 I use the stock pump and a koralia 425, and i personally think 1200 GPH would be too much, but thats not to say you couldn't make it work. I can tell you that both my return and powerhead are aimed into either glass or LR to disperse the flow, and even the part of the tank with the slowest flow where i have my long tentacle plate coral is still strong enough to blow its tentacles around. I have around 700 gph between the two, which i think is about right considering the display area in a BC29 holds about 20 gal of water. it's my opinion that with 1200 GPH going in there, even the lower flow areas might not be ideal for corals that prefer low-moderate flow rates. just my 2 cents!