thanks twigg.
just noticed they want 3 trophic levels, which you prolly cannot pull of in an aquarium. could prolly add an oto or 2 in w/ the snails if the tank is in direct sunlight.
ive tried a plant only tank and little bugs evenually show up and eat all the plants so you'd need something to eat the bugs.
maybe start w/ 3 MTS, 2 oto, 2 Cherry Shrimp and tons of plants in a 20gal w/ direct sunlight. If youve got a male and female of each, any breeding would eventually produce the max sustainable level w/out addition of food.
water changes would be required.