This purple growth is Cyanobacteria, often thought of as algae, but is in fact a bacteria that uses photosynthesis for energy. It is commonly referred to as “Red Slime Algae” even though the name Cyanobacteria translates to “blue-green”. Despite the name differences this bacteria can span the rainbow of colors, not just purple as seen in our tank below.
Cyanobacteria can be brought on by improper lighting or excessive phosphates and nitrates. Since we have very good lighting in our tank, I doubt that lighting plays any part in this breakout. What we do suspect, however, is phosphates since we currently see diatoms present as well (see “Diatom Bloom” post). This spot of Cyano has not progressed or receded in the last few weeks. Along with our diatoms, we will watch this cyanobacteria and make treatment adjustments based on further growth or recession.
One thing we did adjust recently was the powerheads in our tank to create higher flow. Doing this decreases the amount of CO2 present in the tank, which algae like to consume.
A word of caution for those wanting a saltwater aquarium: It seems that if it isn’t one thing, it’s another. It is certainly not for hobbyist that simply want to watch a few fish swimming around. Owning a saltwater aquarium takes constant vigilance, persistence, and not to mention interest. It’s not possible to have a successful saltwater set-up if you have no interest to research all of the little things, like this little spot of Cyanobacteria, that pop up. These “little things” can get out of hand very quickly and wreak havoc on a tank and its inhabitants. All in all this hobby suits my husband and I very well. Between the two of us we can keep up with the maintenance, testing, research and treatment, and still maintain interest and enjoy the hobby!