I'm sure this is probably been discussed. But I'm lazy I didn't want to search lol. I just upgraded to a 125g. I'm using 2 cascade 1000 canisters currently, its working very well actually. But I have a spare 20L that I'm kicking around the idea of using as sump for the 125. I have a few questions, I've never used/done a sump before. I understand the concept... Would a 20 gallon sump be enough or more beneficial then my two cannisters? If so I plan on doing a non-drilled setup, is there a common way to do the overflow? Lastly pump size? Thank you in advance!