I added the CPR medium fuge for my 20 gal. I LOVE it. 2 months after adding it and it is TEEMING with pods and worms. It is filled with cheto and had an 18w PC light over it. I had a cyano problem before I added it and now... Poof, no cyano.
Also, there is just enough room in the first part of the fuge for a Lee's airstone driven skimmer... which I added. That was the second best thing I ever did for the tank.
The only issue with the CPR fuge was that when I recieved it, the brackets that hold it on the tank were snapped off. I had do do some creative repair work to get it fixed.
Good luck.