I can’t answer your question, but I do have some comments. I have an Oase SwimSkim. I love it, and it’s great for a small area, smaller pond (your 1000 gallons is probably the minimum size that would work it’s best). When I did my research, I realized that the AquaSkim needed a pretty much flat and level pond-bottom in order for it to work properly — and there is a minimun-maximum depth requirement for both skimmers. My pond did not have a level bottom, and I didn’t have a spot that met the maximum depth, so the AquaSkim was out.
As I said, I love my SwimSkim, and though it in no way functions as well as a built-in skimmer would, it is better than not having anything. Plus, it has a feature that also aerates the water! I have had it for 7 or 8 years and have never had a problem with it. The Oase people have great customer service (or did, the few times I had to contact them). The only issue I have ever had is that occasionally (IOW, if the filter pad gets overloaded) it will pop up. The solution was to place a small rock (experiment) inside the basket.