Hi, there are some good threads I saw on this site which might be helpful:
Opae ula shrimp living in their natural environment caught on video.
Natural Environment for Hawaiian Opae Ula
Natural Environment for Hawaiian Dwarf Hermit Crab and Pipipi Snail
Interesting videos that contain Opae ula shrimp.
Interesting documents, articles and pdf's.
The pdf I posted in the last thread says the following: 'In upper, sunny water, green Chaetomorpha and Valonia may carpet rock walls down to 15-20 feet. Below this depth red algae, such as Hildenbrandia, dominate. The indigenous aquatic flowering plant, Ruppia, or seagrass, sometimes grows luxuriantly on pool bottoms.'
Chaetomorpha is easy to get. Valonia is regarded as a nuisance algae in reefs, where it is known as "bubble algae".
This person says he found a source mentioning "Enteromorpha (A tubular form of Ulva), Cladophora (Likely C.prolifera as opposed to C.aggregans, the freshwater marimo algae,) and Ruppia maritima":
http://www.google.com/discussions/vi ... php?t=4216