I have two on my 90 gallon. They are being controlled by my Neptune Aquacontroller III. I think they are great as far as flow goes. They really get the flow going. They have a knob that controlls the speed of the propeller so the flow can be turned up or down. I did have some issues with a couple of fish being sucked to the propeller housing. It occurred while I was watching, so I was able to free them. See this link:
WARNING! Eco
I have since removed the filter floss from around the pump because it was cutting down on the flow. I have not had anymore issues. Perhaps the fish have learned to stay away from them. Another thing is that because my pumps alternate on/off, when one is off, it gives snails time to climb inside. When the pump cycles on, the snail jams the propeller causing the pump to over heat. When the pump over heats the outer pump disengages the inner propeller housing (a safety feature) and it falls to the bottom and the outer pump also falls off the tank. Therefore, the electrical cord must be fastened above the pump, so that it doesn't fall to the floor, causing damage. It is not wise to have anything under the pumps inner propeller housing (fragile tank inhabitants, sessile corals etc) that could be damaged if or when it falls.
I e-mailed Eco Tech concerning these issues and they claim that they would consider redesigning the inner propeller housing to be more friendly to the tanks inhabitants. Don't get me wrong, I think they are brilliantly designed from an engineeering standpoint, but because they are so new all the kinks are not worked out of them IMO. Also, the price is exhorbitant.