I have a little school of about of +/- 7 otot's and about the same amount of amano's in a net 48 litre tank next to 7 pygmaea corys and 15 tetras.. Also rarely throw anything in especialy for the otos and shrimps. When i eat myself some courgette or cucumber i sometimes throw a piece in and take it out hours later still untouched. But i grind down sera vipa chips and spirulina tabs, mix it and feed the fish with this. When its grinded to powder it is dispersed all over the tank and feed much less than if i would use complete tabs. I feed daily 1/4 vipa chip mixed with 1/4 spirulina tab, some parts sink immediately and some parts float for a while before it sinks.. So actualy enough food ends up in the substrate what the tetras don't catch. I notice this with the pygmaea corys, they wake up and get active 3 seconds after the first particle hits the substrate and start feesting and diggin all together about the same time. The shrimps love to run off with the larger grains of vipa chip, this is realy their favorite.
The tank and all the fish in it are about 2 years around now.
Have another 110 litre low tech tank started with 30 cherries and some amanos, gets the same treat and nothing extra for the shrimps.. Now after a year the cherry population at least tripled and keeps growing, amanos are still around. Don't ask me what they are eating next to the bits i feed and i feed very little, i can't realy see it but they constantly are feesting on something obviously and multiplying like rabbits. One day i noticed a fish not doing so well it still was alive when i went to bed.. The next morning i found a it's carcass, or what was left of it.. That must have been a special treat for them it was stripped to the bone with in hours. I also have a pretty low snail population all tho i have ramshorn, common pond snail and Melanoides tuberculata
(all 3 potential pests) and i find plenty empty little snail shells in the substrate, i do not know for sure but i suspect the shrimps and fish keeping also this population in check.
I guess keeping them hungry makes them work harder cleaning your tank and keep the (eco) circle round...