Sounds like the best option is to just utilize a sump? I've been researching them a bit and it seems like building one out of the 20 gal
tank is not outside my skill level.
A revised question would be this - instead of a pump, can I use the canister filter as extra filtration in the last chamber of the sump to create the flow back to the tank?
I also believe the slits in the overflow are at the top and bottom. Im waiting for the weather to warm a bit and im going to fill the tank up with a hose and see how it behaves - as well as give it a good cleaning lol.
Lastly, does anyone know what the device in picture 2 is? It appears to fit into the drain line that goes to the sump. it looks like a float valve of some sort.
Any other advice or recommendations are GREATLY appreciated!