Hi Darren.
Many webpages that I've read mentions Bryopsis as a type of hair algae so I use the 2 terms the same way. In other words, I think of hair algae as a family of algaes and bryopsis as a specific type of hair algae.
For example:
http://www.anchofish.com/cleaners_companion.htm
"Hair algae : includes cladophora, cladophoropsis, derbesia grow fast as a result from high nutrient levels. Another type of hair algae is bryopsis an inch length of feathery dark green bushy species may bloom in aquarium with too little water movement combine with high level of nutrients."
Here's a closeup. They are dark long thin strands of algae. It is not slimy. Its is strong and fibrous. It does have some fern-like tips. It is tough like grass. It doesn't seem as dark and feathery as photos of other bryopsis that I've seen. I have seen my emerald crab eat a some of this algae, whatever it is.
[ 30 April 2002, 09:22: Message edited by: Sam W ]