[Delphinus]

I think the dissolved organics/allelopathy theory is probably onto something there. I've had this same problem with other skimmers as well and the one common element to all the ones that had this problem was they are all meshwheel or needlewheel style, so I think whatever it is, it's something that skimmers that rely on smashed bubbles are particularly sensitive to. Skimmers that rely on foam by crashing and friction, like becketts, aren't sensitive in the same way because what seems to happen for them in most cases is that the foam just stops producing for a little while and then starts up again.

If it is (or could be) a dissolved organics issue then it seems to me the first thing to try would be to increase the carbon. For some DOC carbon does a better job of removing than skimmers are unable to, so it can't hurt in the long run (except you'll need to budget more for carbon but in the grand scheme that's a pretty inconsequential running cost compared to others)..