I MISSED THIS!!!

Random flow doesn't need a fancy controlled powerhead...hex's have lots of angles to bounce current off of silly nilly.

one thing I didn't see mentions is it isnt so much a case of to much flow but how you flow is.

My last tank had a flow rate equal to 125X the size of the tank, my new one I will be shooting for 150X, but while there are benifits to massive water movment you have to do it right.

you don't want a power head like a maxijet making your flow as this is way to concentrated and will kill corals that are to close, what you want is pumps like Hydor Korailia, or tunze which create a large lamaner flow instead of a water jet. the idea is to get the whole water colume moving.
when this is set up right you can have massive turn overs but when you put your hand in the water all you will ever feel is a gentle current everywhere in the tank.

what I would recomend for you is to start of by adding two 425gal/hr Hydor Korailia and play with them to get a gentle flow through out the tank and see how it works for you. that will give you about a 25X turnover.

Steve