I've currently got a 75 gallon tank with mabey 7 med sized rocks and a sand bed. I've got two maxi-1200's and one maxi-600 as well as 2 emperor 400's. So, as you can see, I have lil' bit of flow!
I just got 9 zebra Danios (one of my fav fish) and they seem to enjoy the currents, they dart about the tank, eat like sharks, and in general look healthy. There are spots in the tank with less flow, because of the way I positioned the Power heads.
Does it sound like I have too much flow in the tank for them?