Sure they can. Well, some can. Brian Moss had a wonderful study published on the subject in England's "Journal of Ecology" back in 1973. Some can use bicarbonates and some can use carbonates. Algae are pretty capable little buggers. Some can be grown in complete darkness, and some are C4 plants. Oh man, don't get me started! anyway... Sodium? Buildup? Will mega dosing S. bicarb. accumulate sodium? I am trying to find the answer myself but my head starts swimming when I read sciency people's stuff. I'm not that clever.