I thought that nitrates and phosphates were the primary nutrients of algae. Now I see an article that claims ammonia is critical to algae. Here's the link: http://aquarium-fertilizer.com/nitrate-no3-and-phosphate-po4-dont-cause-algae-ammonia-does My inference from the article is that ammonia in the system would be critical for a virgin scrubber.
I don't know why you deleted that content, that is a very applicable article for freshwater planted tanks. I personally just learned something. Want me to restore the original post?
I reverted it back. It's an interesting article, basically it says that algae spores consume ammonia and algae itself consumes nitrates. The argument, at least for the planted tank, is to prune your plants and provide them plenty of nitrate. The dead plants give off ammonia which fuels new algae (spores) and keeping the plants healthy by providing them nitrate means less plant death and less ammonia introduced into the system. There's likely somewhat of a parallel for saltwater but probably not as direct. However, something might apply to starting out a new screen. If the system is rather devoid of ammonia, then algae spores would not be able to seat onto the screen as well. This might actually explain why some people have a hard time getting algae to start growing (very few instances of this, but a few I was never able to explain). Once the algae starts growing, then nitrate is the "food" and it's not a problem to keep it growing (unless you don't have that either). A new screen that is downstream from heavy filtration might not have any ammonia to access, at all. So starting a new screen at the beginning of the filtration system might fix this, until it gets started, then it can be moved downstream in the filtration makeup.