I've only been growing Monte Carlo for about a year and change, but I have it in a tank that used to run co2, then converted it to non-co2, and in a second tank that does run co2. The plant tends to have slightly larger bright lime green leaves when it has co2. When there's no co2, they tend to get smaller with a darker green color. The growth difference between co2 and non-co2 is shocking. The non-co2 tank can go almost half a year without needing trimming whereas the co2 tank is more lush and happy looking, and needs more frequent trimming almost monthly. In both cases imo, soil is a must. I tried growing it in some spots as an epiphyte, but it struggles. There doesn't seem to be enough nutrients in the water column for me to grow it well without using soil. If you have access to aqua soil, or some other sort of substrate with nutrients, I would suggest experimenting with one of your pots, removing the rock wool, and gently go through the plant and separate it out into pieces. It should be able to break apart into individual stems with some roots on each piece. I would get rid of the melted portions, and just keep the healthiest looking growth. And then plant the pieces close to each other and deep enough that just some of the leaves are popping out. If it manages to spring back, I agree with minorhero that co2 will really be helpful, but not a must.
