...does my skimmer keep going crazy?

It's an Octopus 110. I have it in my sump and it's modded to drain into a gallon milk jug. I have to have the water level pretty high in the sump so that gravity can take the waste to the milk jug, though. Is there a problem with that?

I had it running for a couple of weeks closer to the bottom of the sump, but then realized that the collection cup was getting pretty full before it would start to drain. So, I made a little acrylic stand for it to sit on to raise the hole in the collection cup above the top rim of the sump. I've tried adjusting the water level inside the skimmer, but lately I seem to be getting nothing but clear water. It's been pretty close to filling the jug each day for the last week. Tonight I went to feed my fish, and it had over-flowed so that the wood floor and area rug in front of the tank was wet.
(I don't think the wife was too happy about that! )

BTW, I got the skimmer used, and it pulled out some nice, green, nasty stuff when it was lower in the sump. I'm thinking I should just move it back down unless someone has another idea.