I went to the 1200 also and it took at least a week for it to produce anything. I thought for sure I'd have to go back to the Rio but I really didn't want to so I let it go. Now it works wonderfully, way better than the Rio. Just give it time.
I went to the 1200 3 weeks ago. when my rio 1400 just quit. From every thing that i have herd i am glad the rio didn't foul my tank. it took about a week for the skimmer to come up to full speed but the skimmate seems thicker/drier.