The Physan is intended as a temporary soak to sterilize the root zone. You must also scrub and sterilize any equipment and containers that came into contact with the water. If the physan didn't kill your slime then you didn't use it properly. You must remove dead and dying roots before the soak, throw out the old air stone, ect. The water should get a little foamy or fizzy. Even if the physan did work, the slime is likely to quickly return.
You will have good luck with the EWC tea, however it is still extremely difficult to purge the slime from a root zone once infected. You will need to soak the roots in the physans for 12-24 hours, sterilize everything, and then fill your res with just plain pure water. Add in the microbes and let it set for a day or so before adding any nutes. Even with the EWC tea it is still important to practice proper res maintenance; temps, oxygen, ect. Never add anything organic to the res. Never try to feed the microbes in the res, just add more.
I was plauged with the slime for months. I spent a lot of money on sterilizing products and broke my back scrubbing and sterilizing day after day, and in the end the slime just kept coming back strong as ever. The EWC was like a magic bullet that made the nightmare go away. It did take some playing around with it... I even got slimed again once when I changed the res over to new water (I didn't use enough tea). That time I actually just added more EWC tea to the res and in a matter of 12 hours I watched the slime diminish and get eaten away. Just remember, with sterilizing products or with EWC, root disease will always be there in the background just waiting to gain a foothold and take over. Your best defense is proper res maintenance and good healthy plants. Strong healthy plants will shrug off the slime on their own.
Also, if all else fails, I discovered that plants grown in an ebb and flow type set up don't care about the slime. The res will still get slime in it but since the roots sit in air most of the time, it doesn't effect them.