can you name a good book .. and a link where to get it if possibleIs there a difference between filamentous algae and hair algae or are they the same thing? Technically speaking there is a huge difference. From the perspective of the hobby the terms are used interchangeably. There are good hair algae and there are not so good hair algae, this is where most of the confusion's resides.
There are several species of hair algae that herbivores will not consume, these are the ones that are difficult to get rid of and are the "bad" hair algae. then there are the ones that fish, snails, and other inverts will consumer readily and these are the good algae. The problem comes into play that they all look alike.
Your question was not a simple one, as most are not in this hobby. There are many fine books written on the subject of marine algae. Most are technical and really come down to one thing we need to try and keep algae out of the main tank. LOL