you didnt say its like a SIP did you :O
just fuckin with ya. I'm running them straight perlite, a couple mini ones are coco on top with a perlite res and a couple others are straight perlite with a soil cap (these are going outdoor and I wanted to retain a bit of moisture - probably should have gone 50/50 perlite/vermiculite or coco for this but I'll see how it goes as theres no shortage of seeds to pop).
Also, I'm bottom feeding mine by way of some PVC pipe down the side of the pot so the medium doesnt get build up. Im using the GH maxi stuff and it seems OK so far, Id avoid anything too organic so it doesnt get all filthy in the rez. pH between 5.7 and 6.3 - i vary it a bit every so often by a point here or there to help with uptake. dont know if this works but it hasnt hurt so far
Take this with a grain of salt - I'm no expert on growing hempy style but wanted to dip my toe in the hydro world and this seemed the easiest and cheapest way