Flow rate for overflow, 120g 4x2x2?

BadGaskets · Mar 6, 2024

I'm rethinking my original plan to go low flow on my 120g tank. I was going to go with around 800-1000 gph but I think that's too low. I want to make sure there's good turnover for filtration purposes. My 75g currently runs about 700gph and is stocked with the same sort of fish and I'm thinking maybe I should shoot for a maximum of at least double that.

The tank will be a community stocked with medium sized cichlids and catfish such as firemouth, Severum, and plecos, so definitely not HIGH flow. The plecos would appreciate some flow I'm sure.

There won't be a lot of plants, but Java fern and Anubias (low light, no CO2). Those don't typically want a lot of flow.

What flow rate should I be targeting, maximum? I can always dial it down if I overshoot the flow some, or divert it in a way that avoids turbulence

duanes · Mar 11, 2024

Since severums prefer slower flow conditions, you might be able to get away with 700 gph (5 time turnover) but that's not taking into account head loss.
But 1000gph isn't too much if you spread flow out mitigating the current a little, as opposed to using only 1 concentrated out flow vent.
I use 1500gph pump, and employ a manifold to disburse flow over a wide area the entire width of the tanks surface, because I want as much . surface agitation, for as much aeration as I can get keeping the rheophiles that I do.

Java fern is found in conjunction with water falls in nature, and many plants do quite well in normal or strong flow.