sorry i can't offer you more help here as most of my experience is with outdoor growing operations, though i hve grown it indoors. the main thing is to keep it as dry as possible, get some uv light on there as this kills fungus and mold, and also keep the air cirulating, you may want ot put a fan near the wg and keep the air going as much as possible, fresh air will help too. the grapefruit extract is a good idea. i personally don't do Colloidal Silver
anymore, so i would not use it, but you may have a different opinion on that.
i wonder what affect using ozonated water would have on the wg? i have an ozonator but never used it to water the wg with, hmmmmmm....
also what about oil of oregano? maybe putting a drop or two into the water for the wg would really help as this is a very powerful anti fungal agent, that would probably be worth experimenting with.or even tea tree oil. i really don't know how either of those would affect the plants, but it may be worth experimenting with. just thinking out loud here.
this is an interesting article on wg and mold i found here http://www.gourmetgreens.com/comments.html
In 25 years of juicing
wheatgrass in a variety of settings, I have never seen fresh wheatgrass harvested above mold cause headaches and nausea. In my opinion, the person who wrote that was not interested in learning how to grow wheatgrass indoors without mold and is trying to convince people that outdoor grown, processed and dried wheatgrass products that can sit on a shelf in a sealed bottle are better than fresh. Ann Wigmore told people to just harvest above the mold. Technically, we are talking about slime molds. Slime molds use the plants for support but do not penetrate the tissue. Slime mold is easily removed from the seeds, lower stems, and roots of the plants by simple rinsing. Or just harvest above the mold. The harvested grass should be vigorously green or lighter green near the cut end with no brownish discloration. Ann Wigmore always said that fresh is best. Slime molds are favored by wet environments and feed on dead organic matter. This is why, when trying to prevent mold from starting, it is helpful to not overwater the soil and make sure that there are no small pieces of identifiable plant waste in the soil such as straw, bark or leaves. What appears as mold may also be Rhizopus. Rhizopas sp. is a ubiquitous fungus that grows profusely in high humidity environments. Rhizopus is not pathogenic on wheat seedlings. That is why the growth of fresh wheatgrass growing above the mold is still good for making juice.
Persons who do experience headaches and nausea from the cleansing effects should begin by drinking lesser amounts and eating solid food 1/2 hour after drinking the juice