A Salty Salad, I See
Hi,
The 2-watts per gallon are going to be on the low end, certainly.
The red coralline algae give you bit of a break on the light, the less light the more. Along with macro and micronutrients, you will need to maintain a minimum of 450-ppm Calcium.
I would think one of the Rhodophyta- red algae would be wonderful, perhaps
- Bossiella spp., a genus of coralline algae, very tolerant (comparatively) of water conditions.
- Bossiella californica schmittii, with the reproductive "bumps" (conceptacles is the prper term) on the face.
- Bossiella sp. (Silva) a nice, rather forgiving Red Algae.
Red Gracilaria Algae might like a bit more light and is readily available as it is aqua cultured as fish (human as well, I gather

) food.
Lithothamnion prolifera, any Lithophyllu spp., I suppose these grow pretty much everywhere, even hundreds of meters deep.
If you are able to increase the lighting a bit, maybe another 20 r 30 watts of actinic lighting would be nice.
- Peyssonnelia sp., Burgundy Crust would be worth a try, might be under the bit more light category.
If all else fails, Porolithon pachyderm, Reef Cement will take on the shape and texture of any substrate or anything that happens to be the tank.
I hope this helps…:gw
Biollante