Diana,
The LR would be more for biological filtration, general look of the tank, plus places for pods to live. But if you're running a canister and cleaning it once a week, you should be good without more LR. You have the added bonus of not having a large bioload, which should help quite a bit.
I had lots of macroalgae in my tank when I kept SHs, and had trouble with air building up in the males' pouches. I'm sure it had to do with all the O2 produced during the day and CO2 at night from all the MA. Have read that skimmers might also be a cause, though I did not run a skimmer, so you not running one might be helpful in preventing GBD.
Very cute SHs
