I'm thinking that any CO2, ferts, etc is too difficult to maintain just right with only 1gal (less with wood, substrate, etc.). Too many things can get way out of balance very quickly. I like to keep mine much more simple, and use the plants as suggested above: rhizomers, mosses, moss ball. I have one Gallon vase with pond snails only, and one with 2 RCS and pond snails. One has a tall rock, the other has some spindly wood. I have another home for the shrimp if I've guessed their genders wrong and they have babies. No fert, no Carbon, no heater, air lift sponge filter (I'm not a fan of under gravel), and weekly 20% wc. Lighting by LED 5000k desk lamp, 5hr per day. I trim plants back (mostly the moss) every 2 weeks usually. No algae, slow growth, no plant melting. All seems well.