Leaving unused holes in the AeroGarden uncovered, or covered with clear plastic germination lids, led to rapid algae growth. 3D printing some blank plugs and laser cutting some paper disks to cover the growth medium seems to have eliminated algae growth, making maintenance much easier. Both of these are supplies the AeroGarden originally came with but they've been lost or used up over the years. I'm sure it would be cheap enough to purchase relpacements, but it was fast and easy to make them at home, too, thanks to these tools!