Many people have successfully grown these plants in tanks with C02 and low light, so no. C02 injection is not necessary. If you plan to grow these in an inert substrate like gravel and black sand, I would still ensure that they get some minimal fertilization to ensure healthy growth over the long term. In a 2.5 gallon nano with inert gravel or sand, there is no conceivable way that the waste produced by the limited stock of fish or invertebrates that you can keep will ensure that all your plants nutrient requirements are met. Many of these plants are water column feeders so a good liquid fertilizer should do the trick. Just don't over-fertilize. With such low light, low maintenance plants less is probably better.im currently setting up a nano tank, 12*6*8.
substrate is black sand and some gravel.
planned plants are anubias nana, java moss, dwarf hairgrass, and wallichi.
planned lighting is a CFL 11w.
question is, is CO2 required at this load of lights and plants?