Well, there is a great debate over the "worth" of coraline algae to our tanks. Some claim it can block pores in LR otherwise housing bacteria that process nitrogenous waste. Yet no research proves or disproves this, and in fact such research would likely be impossible since most every system is different. Bottom line, I've seen tanks COATED with coraline that have 0 ammonia, nitrite, nitrate, and phosphate, so if you ask me it can't be all that bad for your filtration. In fact, people forget that it is a photosynthetic organism and as such can bind both ammonia AND nitrate directly. And lastly lets not forget that it only grows where there is light, so the underside pores of all LR remains open for filtration.
Then the only decision is do you like the look and are you willing to deal with the glass scraping if/when you provide truly ideal conditions for it.