Type 1 is fairly common. It’s usually yellowish green and it adheres to walls and floors. It usually does not float freely in the bulk water like green algae. [Edit]- At least not initially. Once it begins to grow, it can float freely and cloud the water. [End edit].
Type 2 is pretty rare. When someone says that mustard algae is rare, this is the type that they’re talking about. Type 2 usually sits on the bottom of the pool. It does not adhere or float freely. It can look like cloudy dust, sand, DE or dead algae.
To differentiate from sand or DE, brush. Sand will billow around and quickly settle. DE will make a noticeable cloud and resettle fairly quickly.
Type 2 mustard will dissipate and resettle in 30 minutes to several hours depending on water circulation.
To differentiate from DE or dead algae, look at the coloring. Dead algae or DE will typically have little color. They will be off-white, gray or light tan. Type 2 mustard algae will typically contain hints of green, olive, yellow and brown.
