I have the Simplicity, and it seems to work well. I have it in the overflow section of the sump though. If you have to keep it in the fuge, you'll have to come up with some way to keep it separate from the chaeto. Can you post a picture? Shouldn't be too hard to DIY something.
Can't really tell from the picture. Do you have your skimmer in the return section of the sump? Where do you have the chaeto? I don't see a fuge light. Can you take a picture of the whole sump?
It seems that the cheato ball is in the top left of the picture. You will need some kind of sponge to keep the cheato out, cheato is like sand at the beach it always gets where you do not want it.