re: Tips for my raised garden

Drain to waste, and I add the castings directly into my "soil" mixture. I use cloth grow bags though, like a smartpot, 2-20 gallons in size depending on the location/strain. It works the same with the larger outdoor beds, but legally speaking they still frown on what I do in my state so not outdoor beds, yet. You can add castings to your reservoir though, but I'd use something like panty hose to keep them from getting really messy and clogging up the pump/emitters.

New batch of castings each grow, but I compost the old materials in between grows. Each batch of soil gets set aside and for about 6 months before it is reused. I add my organic amendments in after about 2 months, and add some mycorrhizae as well. In fact, the mykes are pretty much the only thing I ever add to my water, short of light pH correction. Some folks add a nitrifying cover crop in between cycles, I personally do not.

If I were doing beds I'd just till it into the top couple inches. Also a big fan of adding humates, but my farming pays better so I can buy costly additives. Especially since my soil amendments are relatively cheap when purchased in 50 lbs bags. Most are ground meals, like a blood or bone meal... but I do not use either of those 2 specifically, just a reference. My plants are almost vegan, minus the fish meal I use. I feel the commonly referred term is "recycled organic living soil."