interesting question... i'm going to tag along on this one.. but here's my thoughts..
plants grow faster with co2 because they need it for use co2 during photosynthesis, and while photosynthesizing, they give off oxygen, which is why co2 becomes depleted very quickly in a fresh water planted tank...
the same thing is true about algae and saltwater plants, such as chaeto. That's why when people are having low ph issues one common recommendation is to have fuge lights on a reverse lighting cycle so that as the chaeto photosynthesizes, it removes that excess co2, and adds back oxygen to the water, which in turn leads to high ph.
So my thinking is that co2 will help your algae grow..... however i'm not sure exactly how much... or how practical it is.
In a freshwater system you add straight co2, you don't add it in a liquid form with calcium carbonate.. so i don't know if that would have any bearing on the situation. Also, you don't want lots of co2 in the tank, which is why we point powerheads at the surface, run skimmers, etc.. because co2 leads to dangerously low ph... my thinking is that whatever co2 you are adding via your calcium reactor effluent will be gassed off (more or less) as the reactor effluent hits the water... leading to little or no increase in chaeto growth...
this is just an educated guess here.. and i may be off base..