I’ve been working on kind of a similar project. I have a 55gallon barrel with the entire top cut off and a drain added to the bottom. I filled the barrel with coconut husks, then added about 4 inches of soil. I have tomatoes growing now. It isn’t really hydroponics, but I’m just using the soil for stability and am feeding the tomatoes with compost tea. I water by flooding the soil with about a gallon of tea about twice a week. I run my compost tea maker continuously in another 55gallon barrel. I use about 5 gallons a day total to feed all of my house plants, some yard plants, and my tomatoes in the barrel. I do not buy any additives for my tea. Instead I add just add all of my kitchen waste, about 2 liters per day including egg shells, fruits, vegetables, grains, rice, bread, paper, cardboard, coffee grinds, and tea bags. My tea smells earthy (no bad smells) and is dark brown with a fair amount of biofilm. The idea is roughly based on the organic hydroponic method developed by the National Agriculture and Food Research Organization in Japan in 2005. There is some good info in the references of the Wikipedia article “organic hydroponics”.