I don't use the disk's any more, I buy liquid starter from ReefCrew.
While I grow a lot of nanno, I no longer use it for my tank. Instead, I feed rotifers to my tank about an hour or more after lights out and see better results, especially with corals like the acans.
I no longer sterilize the water I use for phyto culture but when I did, I used to add about 8 to 10 drops of bleach to a 2L pop bottle, fill with tap water, and let sit for at least 24 hours. Then, I add ClorAm-X (or any dechlorinator) until the chlorine is neutralized and then dump half into another sterilized bottle and top both bottles up with full strength nanno that is already cultured.
It was too much hassel to keep sterilizing the water at the volumes I use now so I just take my chances on crashes and if it happens, just restart.
CULTURING PHYTO THE WAY I DO IT NOW