Originally Posted by rob_stl_mo
I figured the more water flow the better. The stand is custom. Didn't think it was the same width. Still new to this
Then measure the stand inside and the opening you are going to use to install the sump and figure from there. If you are unsure, you can simply google "40 gallon breeder tank dimensions" or whatever size tank you are considering.
The more water volume the better, but flow is controlled by your return pump. This can be changed without changing the sump.
You have to figure out exactly what you want to put in your sump, figure the space you have to put the sump, and then choose your sump to accommodate.