A anaerobic denitrator, will remove nitrate ,much faster than an algae scrubber. Given a high ppm starting point. Say the tank is at 100ppm, and you want it at zero.
Now starting at zero with fish adding ammonia daily, it will be a toss up as to which one is bigger, the scrubber compared to the denitrator.
One thing to keep in mind, salt water tanks have lots of coral, and a device called a protein skimmer. Which will harvest the 10 billion, bacteria spawned in the denitrator.
In fresh water, protein skimmers don't function properly. However, the Hydra, a freshwater cousin too the sea anemone, will flurish.
Algae is a much easier, mess to contain.