Help for marine aquarists who have a brown, slimy, or stringy outbreak and want to know what it is before they treat it.
The most stubborn pests in reef aquariums are often dinoflagellates: single-celled algae that can coat sand and rock, trap bubbles, and sometimes release toxins when they die. The right response depends heavily on which one you have, and on whether it is a dinoflagellate at all. A lot of "dino" outbreaks turn out to be diatoms or cyanobacteria.
Dealing with a bloom right now? Read the Dinoflagellate Guide, a thorough, practical guide written by another aquarist, alongside my treatment notes. More on the guides page.
Start with a magnifier
Everyone who keeps a marine aquarium should own some kind of magnifying device. It costs very little next to the rest of the hobby, and it lets you check corals and fish for pests, tell filaments from single cells, and see a lot of life that is otherwise invisible. See the microscope page for how to buy, borrow, and take pictures through one.
Why this site exists
I started with the benthic dinoflagellates because they were the worst pests I kept hearing about, and the guide still leans that way. I add other pest algae as people share them with me. If your pest is not shown here, please send me pictures, a movie, or a sample.
The site is run by Dr. Gregory Mendez, who studied dinoflagellates as a graduate student. It is a hobby project now, and everything here is free.