These photos show some soft coral all covered by hundreds of tiny flatworms. This flatworm can be a real pest, since it covers the whole surface of some corals and thus leaves them no way to catch plankton and their symbiotic algeas (Zooxanthelles) can't produce the necessary sugar. Those corals are slowly dying from starvation.
The photo below shows some acoeous flatworms in close-up. They have a size of about 5mm. Their brown color is from the same symbiotic algeas as mentioned above.
Olypia Maru wreck, Sangat island, Philippines, 16.3.03 and Bali Indonesia 2006
Taken with a Sea and Sea Motomarine II EX , close up-lens and 1:2 lens, F 22 and Nikon Coolpix 5000 in sealux housing and subtronic flash
. Copyright Teresa Zubi