Wow a lot of questions since the last time I looked here.
eldone
I buy mine from
www.OurVitalEarth.com
evagentry
worm tea is only worm manure rather than cattle. This concentrate I use has a shelf life of 9-12 months, whereas your would need to be used in a day or two. Also this company adds minerals to the worm food that puts 76 trace elements into the tea solution. I do not think you can get cattle to eat the rocks. I would be willing to try it if you have it plentiful.
BillC
the big advantage with hydroponic is the absorption that lifts the liquids up to the top keeping roots evenly moist.. Pea gravel would not do this. Also Hydroponic rock is very light making it easy for the roots to grow through it. With Pea gravel I would want to keep the vase full over the roots.