A question about flow


New member
I am trying to set up the return from my sump to get the best flow, in both volume and area. I was kind of under the impression that you wanted about 10 times the volume of the tank, maybe a little more. I hit a couple of LFS this week and discussed my plans with the owners. One told me I only wanted a couple hundred GPH. The other told me that I wanted about 20 times the volume, and one told me that what I was planning would be about right. I realize there are quite a few different opinions when it comes to this hobby, but what is a good number to shoot for in terms of water movement?

I have a 46G tank. The pump I have is rated for about 1050gph, so after head loss I figure I should have around 600gph into the tank. I was thinking about splitting the return to spread the flow around the tank to avoid dead spots. Here is a picture of my working idea:


Does this seems like it should work, or would this weaken to flow too much?should I cut it down to only one in the middle so there is only 3 outlets, or even remove the middle entirely and go with one return outlet on each side of the tank? Or should I go with something else entirely?

Thanks for any advice.


Premium Member
You don't need to rely on your return as the sole source of flow. I'd cut back to just the split return in the middle and add a powerhead for circulation. Less noise, more adjustable etc.


Team RC
Most of us run between 5 and 10 times the tank volume through the sump, the balance of flow from powerheads. Your total flow requirements will depend on what you plan to keep in the tank. 10-15 times is okay for a fish only tank, 20-30 times or so for soft corals, 30 to 40 times for SPS corals is the general rule of thumb.


New member
I would agree with thegrun as well. Run 5-10 times tank volume through your sump and get the rest of your flow with power heads. I'd split your main return into 2 outlets (remove your centre pipe in the pic above). The fewer outlets you have (up to a point of course) the greater velocity of the water exiting them resulting in better flow throughout your tank. Obviously 2 lines pumping 300 gph each will have greater velocity than 4 lines pumping 150 gph each. All giving you more motion in your ocean :)