Referred to as a microalgae, brown or golden algae is actually not an algae at all, but diatoms. What you are actually seeing in your tank are diatom skeletons, all linked together. It can appear as a simple dusting on the tank walls and substrate surfaces, or it can turn into a massive growth that covers just about everything in the tank. This type of algae outbreak typically occurs when a tank is just completing or has finished the nitrogen cycling process, new live rock is introduced, as the curing process can add nutrients when some organisms on the rock dies off, or tank maintenance has been neglected. It is a normal occurrence, as diatoms are one of the first to appear in the chain when the tank conditions are conducive for algae growth, and is usually a precursor to other forms of desirable and undesirable nuisance type green macroalgae.
