Mark,

I would do the following 3 things:

1. Check your RO unit with a hardness meter to see if your unit is due for a membrance change.

2. Start using phosguard again.

3. Increase your clean up critters. I got a couple of lettuce nudibranchs recently and am very happy with what they have done so far. Since the growth is on your glass, snails would be good too.

Gary