I went ahead and tried an Erythromycin treatment.
Im on day 2 now with no signs of stress or negative effects for the plants.
I've got a 20 gallon res on a ebb&flow/dwc/aero/NFT hybrid setup. w/ UV sterilizer in the res.
Feeding with Dutchmaster Gold A&B - Liquid Light and Penetrator/saturator for foliar.
Alot of what I've read is prescribing a 2.5mg / Gal treatment of Erythromycin, however on the back of the box, and just as many articles on the subject they suggest, or "no less than" 200mg/10gal so 20mg/gal . Thats a pretty big difference.
This is the EM that I'm using
http://www.apifishcare.com/products/product.aspx?productid=58
Heres a good article stating 200mg/10gal is safe for plants
http://www.skepticalaquarist.com/controlling-cyanobacteria
I went with somewhere in the middle at 10mg / gal , however I think i may finish out the treatment with the 20mg/gal dose
another thing i should probably note is although i have been battling the slime for almost 9 months now with everything you can think of, including Heisenburgs EWC tea that for some of my older more developed plants worked great for. the younger groups just never got better, most died or i transferred to soilless. My last effort before i was to resort to EM was going to be a UV sterilizer in the res. Which i've currently got and has worked much better than i expected, however I still get a slight biofilm on my hoses in the res and my beautiful white bunches of roots are turning brown, not slime brown but pythium brown. I've removed the Chiller on the res and the water temps are getting upto around 80. Probably warmer in the Runs of PVC that house the roots. I've since add the chiller back into the mix on one group that I"m not using EM on and hopefully in the next day or two (waiting on a part) I will connect the chiller to the EM dosed group as well.
so what i wanted to mention is that I really don't have a terrible case of brown slime. I can tell its still there in the background trying to get a foothold but the UV sterilizer is keeping it down. The EM treatment is really just excessive and mostly just an experiment. I'll post again when i've finished the treatment.