Humbly suggesting quite old Reefkeeping articles as well including this slideshow of the more common and available (at least in US) forms: ReefSlides - September '06 - Algae Album: An Algae ID Slideshow
Algaebase.org is also invaluable but difficult to get much beyond genus level and even that is quite hard.
It is so nice to see macroalgae gain a foothold on UKAPS!
was delighted a few years later to see they were the first to get Halophila ovalis to flower in Europe
In my years of keeping H. ovalis, engelmannii, and johnsonii (now considered an ovalis clone) and others like Halodule wrightii I was always amazed to see flowers form after some near disaster or other. Usually preceded by a random outbreak of cyanobacteria or a temperature spike (such as following a hurricane that rendered aircon useless and drove tanks to 32-33C).
Lovely tank shangman. So nice to see others find the beauty in marine plants.