Since the popular—and excellent— Exaco Aerobin 400 Compost Bin does not have any manual aeration capabilities, drilling holes into the bin can be effective to prevent slimy compost. Drilling holes introduces 3 issues which my STL addresses:

1) The Aerobin 400 has a double-wall build, and space in between is filled with styrofoam. To prevent the compost fluids from pooling between the walls, I designed this hole protector.

2) Compost fluids leaking out of 24 holes will make the Aerobin pretty ugly. :) While this isn't completely avoidable, my design does a great job combating it. The interior of the hole is cone-shaped so water which makes it into the hole will be redirected back into the compost bin via gravity.

3) If your bin is filled with compost, it's almost impossible to get at the 6 holes internally. Therefore, my design can be easily pushed permanently into place from the outside.

EASY INSTALLATION

Drill 8 holes per side. You can do less if you'd prefer, just be sure to measure the holes to be in the same spots on each side of the bin - you'll see why in a bit.

So 8 x 4 = 32 printed Aeration Hole Protectors (or 6 x 4 = 24, or 4 x 4 = 16). I used Army Green Overture PETG and I think it looks great.

To drill the holes into the compost bin here's what worked for me:

First a 1-3/8" or 30mm drill bit to gouge into the plastic a tiny bit. This will provide guidance for a diamond hole drill bit to then finish the job with a clean hole. You'll want to drill all the way through a) outer plastic layer, b) styrofoam, c) inner plastic layer. The plastic pieces will either fall into the compost or between the walls.

Then simply push an Aeration Hole Protector into each hole on the bin. It should "click" twice - first through the outer wall and then the inner wall.

AN AWESOME GRID OF AIR TUNNELS!

Now the fun part. Push a rod into one hole and out the other hole on the other side of the bin.

If you do this for all holes on 2 sides of the bin, you'll have amazing aeration throughout the entire bin (and the best compost in the neighborhood).

Note: Amazon links may be affiliate links which means I'll get a tiny commission on each sale.

I recommend printing in PETG or ASA with at least 20% infill to provide some resistance to the outdoors.