Added a new refugium to my nano

[Roach]

I set up a 7 gallon reef tank about 3 months ago. I put in a bunch of mushrooms that were growing out of control in my main tank. Also some button polyps and a couple of leather frags. There is one maroon clown in there and a coral banded shrimp. Anyway I took an old AquaClear external filter(500gph), took out the media...put in 3" of sand and some macro. Then I put an old 9watt PC from an old eclipse system on top of it on a timer. So far it seems to be working great. Does anyone think that I will encounter any problems with this setup or have any suggetions to make it better. Thanks