We use these in our larger 55 gal + tanks. One is sufficient to provide enough flow to circulate a 55 gallon reef tank. Use two for 65-90 gallon reef tanks and so on. We have been using the same ones for over a year now and they are still running like champs. We have not unplugged excessively to conclude if these have the same reverse flow issue as the smaller 528 gph powerheads. They have been running constant for almost a year flawlessly. Haven't even had to clean them. If you want the top of the line expensive equipment this powerhead may not be for you, but if you are budget savvy and just want a decent powerhead at a great price than look no further.
Tip: Place the powerhead on one side of the tank and point the heads downwards and towards the glass so that the current bounces off the glass (one towards the back glass and one towards the front glass). If you have two of them, place one on each side of the tank and face them downwards towards each other so that the flow currents meet and spread throughout the tank. Spread the heads towards the front and black of glass, but in a way that the two opposite currents still meet. It creates multi-directional flow.