FM, I have the Koolscape. Got if from AMAZON for around $89.00. If you read all the available reviews, you read where people said it pops up a lot. I does. To counter that, people said they either tied rocks to it or put rocks in the basket. I tried that -- kept it from popping up, but also kept it below the water's surface. It was still sucking stuff in, but wasn't "skimming."
Well, I studied the thing [no really, spent lots of time leaning over the rocks, watching it, trying to figure out "what made it tick"] and decided that what the problem was had nothing to with keeping the skimmer in the water, but everything to do with having the "float ring-thingy" do what it was supposed to do. It was designed to FLOAT [duh!] with the water fluctuations [by fluctuations, I mean waves and other water movement] and be somewhat independent of the skimmer and basket. It wasn't doing that. After some trial & error, I found some craft foam sheets that I cut into a "ring" to fit up inside the float part [craft foam comes in several thicknesses]. There are 4 small holes in the plastic -- not sure what they are for, but used a hole puch and made matching holes in the foam ring. IT NOW WORKS PERFECTLY! Well, not as good as a real skimmer, but it keeps the surface crud controlled.
Another thing I experimented with: the hole where the water goes down via the little pump motor. The filter pad that comes with it is about useless. It and about everything else I tried just got sucked down, restricting the flow. I ended up cutting 2 disks of plastic craft canvas and wrapping some fabric netting over those. The netting catches the crud, but the plastic canvas keeps it elevated enough that there is pretty much unrestricted flow.
If I had it to do all over again, I think I'd go with the OASE skimmer, though.