Here's pics. This tank has an internal overflow. I have a eshopps L on a 75 which isn't hooked up just running on air driven filters currently been breeding Turkana jewels for the last 2.5 years in that tank so overflow would be a problem.
Even though this isn't your set up you can do it the same way. That's how I ran the L when it was a faster flowing congo river tank. But reading the other posts that have been added on my trip home I'm starting to think you may have something else going on. Maybe sump is to small to handle the tank volume. Kinda sounds like if you were able to increase water level in your sump problem would be solved? The overflow handles the flow when you turn pump up?
Even though this isn't your set up you can do it the same way. That's how I ran the L when it was a faster flowing congo river tank. But reading the other posts that have been added on my trip home I'm starting to think you may have something else going on. Maybe sump is to small to handle the tank volume. Kinda sounds like if you were able to increase water level in your sump problem would be solved? The overflow handles the flow when you turn pump up?