I've reviewed lots of home-made BSF bucket growing system and I think I've come up with a simpler and cheaper solution to the drainage issue:

I bought a Lowe's 5 gallon bucket and drilled a 1-inch diameter hole in the middle of the bottom. Then I duct taped a piece of square (3x3 inches) window screen over it (leaving the center open of course) and finally I poured 2 inches of pea gravel into the bottom of the bucket.

The bucket sits on bricks to make sure the drain hole is exposed to the air so it doesn't get clogged with soil. I drop my food waste directly onto the gravel, so there is nothing separating the food waste from the pea gravel. My theory is that the BSF larvae won't churn the gravel much, and if they do it will re-settle to the bottom naturally since it is denser than anything else in the bucket.

The 2 inches of pea gravel should have enough void spaces to allow liquids to easily reach the drain hole. I am hoping that these void spaces will trap enough waste that the screen will never get clogged ... but if it does a quick blast with a garden hose should clear it with minimal effort.

Does anyone have any thoughts about this simple new drain system? I'm always looking for simpler and/or cheaper solutions so I hope this one works.

I just drilled small holes in the bottom of mine. I only lose a few babies, sometimes. They seem to stay around if I keep feeding them.

After several weeks of using a screen to cover my center drain hole I get the feeling that your technique of drilling small holes in the bottom might work every bit as well as mine. I say this because some of my little guys squirmed out through my screen anyways.

One thing I have learned these past few weeks is that my 5 gallon bucket is way too small for establishing a large colony. As soon as I get about 6 inches or more of "grubs and other stuff" in the bucket I no longer see the grubs. They definitely churn the pea gravel though, and this is something I did not expect. In fact it appears that most of the more mature grubs live in the pea gravel layer whereas the youngsters are found mostly in the garbage on top.

Fortunately I have an old bathtub out behind the barn, and I think I can use it create a much larger home for my grubs. There's already a drain hole in it so I will use my screen technique to cover the drain. This is easier than drilling a bunch of holes in the steel tub bottom, and besides, I want to catch the excess fluids in a bucket rather than let it drain out all over the soil beneath the tub.

I was thinking I would nest two Lowes buckets and drill small holes in the bottom of the upper one and attach a hose to drain from the bottom one, much like many of the commercial worm bin designs. (alternatively, I could just pull the upper one out of the bottom one and dump it).

I was thinking to line the upper bucket with a layer of coir that could then be composted in a worm bin and replaced as needed.

Any suggestion about diameter for small holes to maximize drainage while minimizing migration/loss into the liquid below?

owkaye- Thanks for your post. How did your screen technique work out?

I'm half way through with my larger BSF system. I have a 55 gallon plastic barrel cut in half long ways. This half of the barrel will be placed at an angle in a wooden box that I already built. A metal grill will sit in the bottom and I was going to use window screen to keep the compost material in place and let the BSF juice drain.

Do you know if the BSF's are more likely to go to the top of the compost pile if its dark?