Yes but how many problem species of algae are there? Maybe 5-6? I'm talking about BBA, staghorn, oedogonium, spirogyra and the like. GDA, diatoms, and GSA are all easily solved with simple adjustments. However these filamentous types are a very permanent fixture in a tank once established. On top of that they are very hard to introduce via spores and instead normally colonize from cells hitchiking on something. A systemic dose would wipe out (it can also be done successively) each species of nuisance algae and while the tank may be "out of balance" there will be no one to fill the niche. Or rather no one glaringly visible.