I had the ETSS Sump Buddy 40 and powered it with a Mag 7.
I too had a space problem so the SB40 seemed like a good fit.
Here is my experience with this skimmer-
1. It is very sensitive to water height, so you will need an ATO if you want the skimmer to run at its best.
2. The skimmer will stop skimming if you put your hand in the display to move rockwork, or clean the tank.
3. The skimmer will also stop skimming when you feed the fish. I found it took about 1 hour for the skimmer to get back to normal.
4. Be careful when looking at the advertised small blueprint with this skimmer. When you take into consideration the pump (Mag 7 or higher) it actually takes up more space than you would expect.
5. You will need to add about 4 feet of hose to the air line to quiet the skimmer down.
Well that said after about 3 weeks of having this skimmer I decided to sell it and get a Tunze 9005. The Tunze has a built in pump and really does take up a small amount of space, and is dead quiet. And as an added bonus it does a great job skimming
Good luck with your decision. Hope this helps.