Microcladia coulteri grows epiphytically, which is to say it grows on other algae. It grows predominantly on large red algae, and occasionally on large brown algae, and here are some examples of algae it grows on in Monterey Bay, CA.
Here a tiny Microcladia coulteri grows on a smooth, nonreproductive blade of Chondracanthus.
(Left) A long, elegant specimen of M. coulteri.
This beautiful specimen of Chondrocanthus displays the bumpy reproductive growth that lends it the common name Turkish Towel.
Check this out: Not only is this huge blade of Chondrocanthus completely reproductive, but also the Microcladia growing on it is so dense it looks like hair!
A really tiny specimen of Microcladia grows on the tip of a branch of Sarcodiotheca gaudichaudii.
The whole specimen of Sarcodiotheca.
It is difficult to differentiate between the Microcladia and the Prionitis linearis, in this picture, but the Prionitis has thicker flatter blades, towards the bottom, and the Microcladia is exploding in feathery bunches towards the top.
Here it is perhaps easier to see the delicate Microcladia growing on the branch of Prionitis.