When you trim the moss, turn the filter off. Then trim the moss and once your finished trimming use a siphon to suck up all the little bits that float around.
I wouldn't mind some Hyphessobrycon amapaensis (Red Line Tetra) it's on the allowed list
and Nomorhamphus ebrardtii (also on the allowed list) cause they would be freakin awesome to have, although I would need to get a bigger tank.. hmmm
Why not use A Soda Stream CO2 system. Use the search function, there is a lot of information. This system will be cheaper in the long run compared with the Hagen Nutrafin Co2 system.