Sand and Airpots?! ehh? (critter barrier)

When growing in organic coir I had thrips, fungus gnats and ants. Topping with perlite seemed to help. DE can cause drainage issues.

I also used no pest strips... not exactly organic but worked.

If they have easy access to organic material/water it's a losing battle using almost any product/tactics for air pots. The tights sounds like the sexiest idea ^^ since it should hinder adults flying in/out of the holes. You're seriously wasting a lot of energy otherwise, since battling gnats will counter the air pots upsides to the point you're better off using traditional or perhaps fabric pots.

Try a 2 inch layer of ''normal'' coco/perlite as a barrier over your soil. If you are watering at the most every other day the coco barrier will dry out fast, it doesn't make a good home that way since you have blocked easy organic materiel/water access. It's not an absolute pain to re-hydrate either. Or try that last if you prefer products.

Almost forgot to mention. If you are using organic based feed or adding additional ''top mulches'' the coco layer will not work as well if at all. You need to put up the barrier then limit as much as possible any additional organic material put on top. You can use monthly top dresses, or ''water ins'' (again don't go over board) you may see a little spike in activity but it will pass pretty fast with the coco wet/dry cycle.