Hydor Fan Noise


Reefing newb
I have 2 hydor 1400 circulation pumps connected to a hydor smart wave. When the fans startup, they make a knocking noise that scares my fish. I called Hydor and they that it is just the way it is. Nothing can be done.

Make sense?
Thanks, it is quiet enough when running, it's just the starting thumps. (Noise from overflow and skimmer drown it out :))

The insulting thing is the guy at Hydor insisted that it was because it was AC motor and it would only happen every other time. He didn't want to listen to the fact that I said it happens EVERY time it starts.
I think we are focused on the wrong thing here. The hydor pumps are designed to be on. It's when you introduce the smart wave system that destroys the pumps. There is no ramp up and straight 60hz that kills the pump. I agree with aquarian, jebao pumps are great pumps and my opinion is so are the noisy over priced vortech. That was a tangent, get rid of that hydor smart wave which is the same price as the jebao. Sps loves the pulse pumps.
Mine did the same thing when wave controller was switching over. I had the same setup with 4 Hydor 750's and they knocked when restarting. As reefer rob mentioned watch out when they start backwards. Twice I came down in the morning and found my yellow tang stuck to one of them running backwards I thought for sure it was a gonner when I found it. But it is still alive and doing very well. I have since switched to 2 Jeboa powerheads with the twin controller, working great and no more starting in reverse.