This one has been up for about 8 years and hasn't given anyone any problems. There was one air stone originally, and after about 6 years it sunk down in the muck or got covered with vegetation (we're guessing)so not bubbling as much as when we put it in.
We added a second one along with a splitter valve a few weeks ago and placed this one in a bucket with a rope and float so we can pull it up if needed. Still have to go fishing or deep sea diving for the other one!
Overall, I like it. The only issue is it comes on when the wind wants it to and there's no way to control that. We do however, get a pretty steady breeze there on most days, and it doesn't take much wind to get it bubbling. I wasn't around when it was installed so no input on that.
