Here's mine I made from 18 gallon totes
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I just did the same living soil mix I've been doing all this time. I use plain water. I got some malted barley seed and mixed that in the soil for enzymes. I use just plain water. I have an air stone in the resi too. I did add worms to the sips too.
Some people add labs to theirs but you can't use an airstone with labs.
Great minds think alike, I got an air stone in mine too
, i'm making a malted barley enzyme tea right now and holy crap is this one foamy and milky, I just rinsed my sprouted seeds and they foamed up so hard looked like they splooged in the water. My box came with this grate and I just put dirt ontop of it, I hope I did it right, I packed the corners hard, it was wicking up when I was testing it out. I'm using R/O water with some bene's in it to avoid root rot, I like the worm idea as well
, 18 gallons sounds beastly, the one I got fit a full cubic foot bag of soil than had room to fit another half bag so about 1.5 cubic foot of soil in the top half(about 12 gallons of soil give or take a gallon or two) and 2 gal in the bottom