There are so few of them in there right now that they've got more natural food than they can eat. Even if all 12 are still alive, they've got about 12.5 square feet of surface area to feed from counting the substrate and leaf and wood surfaces. Once there maybe 50 or so more in there then yes, I'll have to start feeding them. Thankfully I know a lady who knows a lady who keeps a lot of different kinds of shrimp and has food. I'll need to get a population of MTS going before all that so the pest snail population doesn't explode like it did months ago as well as risking secondary pests. Bottom feeding fish are out of the question due to the destruction the last ones wreaked.
Back when I had my highly successful colony of RCS I settled on much longer photo periods and fed very sparingly. Once I had hundreds I would split up a single algae tab every 2 or 3 days. I didn't have fish in that tank, but I had a good population of Ramshorn snails. That was the most successful self sustaining tank I ever owned. I went several months without water changes and noted that there was more prolific breeding...
I started with about 20 or 25. Fed a small amount daily and manually removed what was left an hour or so later.. weekly water changes.. shorter photo periods... it was like the tank contradicted every accepted guideline to which we adhere.
I even removed eggs from Corys and Angels and dropped them in there and pretty quickly had to scramble to find homes for all of them.