Yes it was co2 and a while rather a tad more light than low.. More like medium.. But also had MC in a low tech, remarkably enough in a shaded spot almost in the dark at a cave entrance. It didn't realy grow much but stayed alive for a year, till i accidently vacuumed it out. Never did put it back.. MC can be a slow starter, but once it sufficiently rooted it takes off with co2... As far as i know it'sone of the most favority low light carpeting plants. Hair gras can also be an option, but also darn slow but nearly indestructable in my experience.
Akadama is an ok substrate, tho the larger grain >3mm is difficult to penetrate because the coarse grains kinda hook into eachother. Need quite some force to plant bigger plants with roots.. If i would choose it again i would go for the finer grain available. No larger than 1-2mm. But it is a pretty stable long term substrate, at least as far i can say for the 2,5 years i have it in the tank. If it's still solid after all this time, why not longer.. We shall see still going strong and not done yet.. It grows plants realy well. Pitty it doesn't come in black or darker, personaly don't realy like the color. So i caped it. In the other low tech i used Fuji sand, which is rather hard to find, had to order it at a Bonsai shop in germany. This is black, but relatively hard crushed lava rock, but less porous then regular lava substrates. No ide why they call it sand.. The Bonsai enthousiasts wonder why it's in the trade. But it is and also grows aqaurium plants realy well if clay is added. Because it is rock, it will still be rock in a 100 years.
But don't ask me about substrate, i'm as anti fertilized substrate as someone can be.. I do not have experience with it and never will.Tho if so i'm leaning towards a combination with clay cmpost based pond soils and something inert.
Experimented with that, only placed it where the plants root. It was an Eureka! Imho.
What i sometimes do absolutely not understand in the scaping hobby.. And seen it quite often.. Someone puts in 15 litres of ADA Soil and than plant 80% epiphytes..
Mysterious isn't it, could have saved 80% of the money invested with thinking twice.
But that's just me.. I guess..