I'm having the same probs I think.

The set-up:

- DWC bubbler (4 x 6" airstones)
- 6 x T8 fluorescent lights (warm and cool mix)
- nutes: General Hydroponics flora series mixed to the correct ratio (or so I believe) for seedlings
- pH is just under 6.0
- room temp is 70-75

As you'll see, there is some brown ick starting to develop on the roots. This ick appeared just after the first nute change (10 days after the plants went into the bubbler). When I noticed the brown I drained the system and gave the bucket a good clean with a bit of chlorine bleach solution and then rinsed it thoroughly.

I then refilled, adjusted the ph, added the nutes and now I'm waiting to see how things progress.

It wasn't until after I had done that that I read about adding H2O2 to the system and letting it sit for a day to try and stave off what I presume is algal growth.

Three questions:
1) Should I empty the system once more and go the H2O2 route ?
2) If I do, what is the recommended ratio of hydrogen peroxide to water ?
3) Instead of H2O2, is there a recommended microbial additive I should use to kill off the algae without harming the plants ? I have read through a number of posts but couldn't quite tell what was the best route.

Thanks in advance!
Peace everyone.