Hi If you dont want C02, carpets, can be difficult. Hairgrass belem/jap hairgrass (whatever you wanna call it) does well, stays low, and carpets well. Normal hairgrass might get a bit long, but will still do well. That said though, if you have time on your hands.., you can try getting lil squares of Stainless steel mess and affix moss to it, and lay them down into a carpet... (im personally doing it with riccia on flat rock, mesh might need to be held down...) Honestly, stay away from HC/HM/Glosso. they all dont NEED c02, but thrive under c02, and hard light. My suggestion would be: Stainless mesh squares with moss (great for low light) - Fissidens or willow moss would be great! Basically anything else which is "low/medium" light requirements. Go speak with Liverpool Creek, he will not only give you GREAT advice, but also an amazing deal! (Currently 6 species for 25 or something... my LFS cant even do 4 (with a good range) for that cost.. and the quality is 100 times better! )