This was my weekend to clean equipment. So, among other things, I took apart my Hydor slim skim nano, soaked it good, had it shining like a new dime. Re-assembled it, put it back in tank; no foam, just air bubbles everywhere. Got out the instructions, took it apart, reassembled it--several more times; same result. I'm not usually given to gratuitous profanity, but I was close, very close. What the heck, I'll just do without a skimmer, I figured. It's a small tank. Took the nano to the garage. Whereupon my wife says, "Hey, do you need this piece of plastic you left in the bathroom?" Of course it was the front plate to the skimmer, in all its lonesome glory. It had never been put back in the half-dozen times I had torn the skimmer apart trying to "fix" it. "Yeah, I might need that." Reassembled it and in short order the nano was a foam-making machine once again. Apologies to Hydor and Foster & Smith (who sold me the thing at a discounted price) for wrongly calling into question their parentage. And to all the deities I might have offended: "It's Lent; I'll make amends."