S-M-R-T, I am so smart.

Well, the vinegar did the trick on the protein skimmer, and now it's all shining and new... with one little problem. You're supposed to run non-vinegar water through to rinse the thing out. So, we did.

(Quick protein skimmer background, before continuing the story: The way the thing works is it sucks in water through a big pipe, air from a little pipe, and churns them together with a motor to make very fine bubbles. All of the nasty things in your water stick to the bubbles, which rise up a tube to form foam. Then, every few days, you skim off the top few inches of foam, and thus all of the nastiness. Voila, clean tank.)

Our formerly foam-producing filter suddenly only spat out large bubbles. Kevin (aka, Mr. MIT Electrical Engineering degree) spent a long time playing with it, not wanting help, only to decide that somewhere along the way we must have lost a spacer and the bubble motor was now positioned too far forward to work. Sadness.

So, fast forward to tonight, when I was reading the fish book where it talks about filtration. It mentioned that protein skimmers can only be used in marine tanks because there isn't enough surface tension in non-salt water to form the fine bubbles that make the contraption work. (Vinegar also provides this surface tension, apparently.) Mystery solved! And I found it! :-P It's nice to come up with the answer sometimes.