Kim Andi

We just figured out we had algae in our spa as well. The main reason is the extremely hot weather that we've been experiencing (high 80s and in the 90s) and it's the hottest summer that I've lived in since I've ever owned my first hot tub in 2001. It's kind of funny too, that the first thing you would see in a lake or pond is algae, especially in the summer. I'm going to shock ours since we just got it filled about 2 weeks ago for the first time and hopefully that will do the trick.

In my personal experience, it's better to have a little higher alkalinity - it will prevent folliculitis: http://en.wikipedia.org/wiki/Folliculitis

We have a spa that seems to have the type of opening you have, are you sure the entire housing cannot be moved into the tub to access the filter better and then put in the Nature2 cartridge?

When I read about the Spa System Flush today, the description indicated to use it just before you are ready to empty your spa and refill it. It is supposed to do exactly as you indicated, but the next step is to empty the tub and refill it with fresh water. And I think there was something about MPS too, not sure though.