Invert tank maybe? Help me "stock"

Apple snails (adults) need about 2.5g of tank space per snail, dwarf shrimp about 10 per gallon (adults) but leave LOTS of room for population explosion. Although apple snails and shrimp don't bother each ohter, one thing to consider is tank maintenance. It can be challenging to gravel vac a shrimp tank, but apple snails are relatively high waste producers. I do it in several tanks, but it requires a good maintenance routine. Temps should be low to mid 70's, the higher the pH the better for the snails shells (over 7.5 is best) which limits your range of shrimp choices. Most neocaridina do fine in this range. A sponge over the filter intake and a cover on the tank are important for both. Food for snails should be calcium rich foods (there is a stick at the top of the section) and for shrimp they are omnivorous, i prefer crab cuisine (made by hikari) because its small pellets and easier to not overfeed.

i wouldn't put more than 4 adults.

I have a 29 Mystery Snail only tank and I would recommend lots of live plants. Hornwort and Anubias work well.

I agree, fast growing live plants like anacharis and hornwort help to absorb excess nutrients and the snails like to hang out in them and graze on the infusoria.

hmm, any chance I can put 30 adults in a 20g