Sure thing, man
Just a point to note... Make sure that you have some way to keep the mess off the bottom, and strained out. Even if you put cheesecloth or something in there - which you'll want to do - if it fully touches the bottom of the container, it will just clog/seal it, and prevent drainage. There are multiple ways to get clever with this, but make sure that you do. Because you're right, the big bang from this method, is capturing that liquid gold.
Microbes are definitely your friend, but so are fungi. That is almost certainly what is creating your monster growth. The leaves and straw/hay are culturing a web of fungi, that form a food chain with the plants in the root zone. You will literally never need to fertilize that garden, if you keep going with the method that you've chosen. This is why we sometimes say around here, that the best garden is a soil garden with lots and lots of organic matter added in. It's just unbeatable.
I'll pick up some elastic top 5 gallon paint strainer bags when we go to town tomorrow. They have them for cheap at Lowe's. Then I'll start getting some of the water out of these buckets.
The more I learn about the BSF larval colonies, the more I wonder how this ever happened in the first place. Supposedly, the BSF female doesn't actually lay eggs on or in bad fruit but in a protected area nearby. I never put anything from "nearby" into the bucket, only the reject peppers and tomatoes that I've been collecting every time I pick. The eggs had to come from those since this occurred in an always covered bucket. Even stranger, it's still going months later with no more input except for the fruit that isn't up to my standards. So it seems like a lot of eggs are going into the bucket from somewhere. I'm trying to verify that now by starting a new container with some bad fruit from the garden.
I wish I hadn't dumped in all dried grass clippings but when I stir and drag those clippings to the surface, they're filled with crawling larvae. Even in the bucket that has 18" of slop in it. Go figure.
Another thing that doesn't make sense is BSF supposedly loves manure but I've never seen them in manure and I've been composting that for many years. I just went out and dug around in a big pile of composted horse manure from last year. Maybe it's too well composted to interest them now. It's still moist at the bottom and there are other bugs but no BSF larvae at all. I've also never seen them in my usual household compost pile.
Do you know what happens if the high microbe liquid removed from the buckets is stored in sealed jugs? I have no clue if the good stuff would die or multiply. I imagine if it's sprayed out on the ground at 30:1, the microbes will multiply like crazy in the soil but my ideal scenario would be to store it and do a massive application when the crop is done and I get to work on the next year soil.
When you catch the escaping crawlers, do you try to hatch them into actual flies?
First time I heard of BSF was from a guy who raises them to feed to his chickens lol. Still, I thought you might find some of his experiences helpful.