Hey there Nacl. I got mine the same day that you got yours. I cleaned my collection cup out last night. It did not have any water in it, but it did have the beginning of some "gunk". I would raise the prefilter part like the manual shows. I have mine high enough so that the bubbles reach 2-2 1/2 inches into the cup portion. That way, water does not flow into the cup and neither does the foam. If you have any problems, let me know. Or call euro-reef (their # is in the manual.)
Good luck.