Flow problem.... too much?

I have a 170g 72 x 18 x 30 tank, which has been up and running for a couple months now. As I slowly add residents to the tank I'm noticing the flow is considerable, and is bothering some folks. The pump is a mag drive 1800gph pump and is really scooting some pressure out the return nozzles. I also have two tunze powerheads, also.



What I'm seeing is that my maxima clam in the middle of the tank, on the sand bed (attached to buried rock) is not liking the flow, and neither is my long tentacle and sebae anemone. They have moved around the tank considerably, trying to find the 'sweet spot'. The feather dusters really aren't liking the flow, either. Currently have only a couple fish in the tank, as the load slowly increases, but they have high/mod/low flow areas, they seem to enjoy, but I don't have things like butterflys in yet, which wont like the high flow.



I do have a valve just above the return pump in the sump, in-line and prior to the nozzles, and was thinking I could just close that valve down a little to cut flow to the nozzles slightly, and that would help. The down-side to that is restricting flow like that will lead to premature failure, in my thinking. Am I wrong, and closing that valve a little won't kill the pump?



Do I have too much flow going on? What do you suggest?