No it is not foaming, just normal aeration bubbles when the jets are on. What kind of "thing" might be growing? Ewww! We just drained the hot tub 2 weeks ago and flushed the lines, which we do with every water change. My husband removes every last drop of water when we do water changes. We bought a hose-end charcoal water filter, which we used this time when we refilled the hot tub and put new filters in this time as well since we were switching from a Blue copper system to the salt system. The water is crystal clear (in fact, clearer than I think I've ever seen it). I called Spa Depot yesterday, where we purchased the Saltron from, and the guy told me to add 1 ½ capfuls of Oxy Spa to it "to activate the chlorine," which only temporarily raised the chlorine levels. When I checked it again this morning there is nothing registering again on the strip. It jumped to normal levels after I added the Oxy Spa. We are now running it 4 hours a day (they told us to turn it down from 7 hours, which is what we were running by the end of last week with still no chlorine registering on the strip. The generator is producing the fine bubble mist when running and appears to be working fine, but we just aren't getting any chlorine rise, it's so weird.