We've learned from many wheatgrass sellers that the mold is very common-- almost every wheat grass plant that I saw at my local pet shop had a little white fuzz. All of the providers have told us that this "spider mold" is not harmful and after further research we've learned that it can simply be rinsed away. It's the same type of mold that we breathe in everyday.
All this said, there are different types of mold and different things that we may describe as mold. The non-harmful mold that I describe above looks like cottony white fuzz growing up the shaft of the wheat grass. If this same "spider mold" is spotted on the seed then it is in fact NOT mold. Instead it's a sign that the seeds are drying out. It's perfectly normal for some of the seeds to fail to germinate, but you can always mister or water the top seeds in the future if your home is a little dry.
Here are some helpful videos to assist you with cleaning your tank and growstones:
Feel free to pass along photos of your plants and Water Garden if you have further concerns or questions. We're happy to check them out and provide additional information and/or support.
Happy Water Gardening!