Hey, that's a coincidence! I just completed adding a sump to my 30gal...a very similar situation.
Even having done it, I don't know what my GPH
actually is. I learned a lot about head pressure. In my case, I needed a 750 GPH
pump in order to get an estimated 300 GPH
actual flow. That's key... you can't determine what GPH
you are going to get from a pump just by looking at the rating. You need to estimate your head pressure, which reduces the flow accordingly.
In the end, I had to throttle the pump back slightly because I was pushing my overflow box a bit hard. So I might be at 200 GPH
. The tank could easy take more than that. It isn't like 200GPH is causing too much water circulation in the tank or anything.
I also have supplemental 60GPH power head in the tank for additional water movement. If it didn't clutter up the tank, I would consider even another powerhead in the tank.