I agree with Aokashi, those plastic pots filled with gravel would actually work well, or just simple small clay pots. Then you would easily be able to move the plants while cleaning, still have a bare bottom, and the plants can root.
THere is no need for liquid CO2, not sure why you keep insisting lol. Co2 will naturally form by the waste. The only thing I would recommend is a fert for plants to grow.
I would skip hornwort, it is super messy and not worth the extra cleaning, anacharis, java fern, anubias, wisteria, and a marmio are all good plants and can be found at stores like Petco or Petsmart.