Red Slime Algae

Cyanobaceria, also known as Red Slime Algae is typically a reddish-maroon colored bacteria that grows on Live Rock and Live Sand. Red Slime Algae grows rapidly into small mats, but is easy to brush away or siphon out. It is normal to see a small Cyanobacteria bloom one to two months after moving or starting saltwater aquarium, but continuous algae growth should not be present after three months. If it keeps growing, then it is time to take action to eliminate it from your saltwater aquarium. To grow, Cyanobacteria require light, nitrate, phosphate and carbon dioxide.

Red Slime Algae

In general, Red Slime Algae is caused by excess Dissolved Organic Carbons or DOC’s in the water. The most common reasons for having too many DOC’s include overfeeding, lack of filtration and the use of tap or well water for water changes or evaporation top off. In simpler terms, more waste is being added to the aquarium than your filtration system can remove.

Prevent Red Slime Algae

1. Use RODI Reverse Osmosis water to prevent the introduction of phosphates and nitrates. Typical tap and well water has a TDS, Total Dissolved Solids, of 250 to 500ppm. TDS is how much stuff is in your water. This includes copper, chlorine, phosphate, silicate, iron, zinc, lead and nitrate. After RO purification the typical TDS is between 5 and 10ppm, and after RO Deionization purification it is between 0 and 5ppm. As a result, algae has 25 to 50 times less nutrients that it can use to grow.

2. Reduce the how much and how often your feed your aquarium. Stop feeding pellet and flake food. Instead, use high quality live or frozen foods as they have usually contain less phosphate and nitrate.

Eliminate Red Slime Algae

1. Weekly 10-25% water changes with reverse osmosis water. Using tap or well water will only make the problem worse.

2. Use a GFO (Granular Ferric Oxide) like Phosban to remove phosphate from the water.

3. Increase filtration by adding a Protein Skimmer. Do not skimp on this piece of equipment. Buy the best your budget can afford, so you don’t have to spend more money upgrading later.

Control Cyanobacteria

1. Increase water flow, Cyanobacteria likes to grow in low flow areas.

2. Add a clean-up crew. Some hermit crabs and snails will pick at Cyanobacteria, but the best herbivore is a member from the Strombus family, like a Fighting Conch

3. Add a Refugium and macroalgae to compete with the Cyanobacteria for nutrients. Popular macroalgaes are Caulerpa and Chaetomorpha.

4. Turn off your lights for three to four days. This will eliminate most of the Red Slime Algae, but it will grow back quickly if DOC’s are not reduced during this period. Also avoid direct sunlight.


5. Use a commercial Cyanobacteria remover, like Chemi-Clean. Red Slime Algae will continue to grow if DOC’s are not reduced during this period.

To control and eliminate Cyanobacteria and Red Slime Algae you must reduce the amount of DOC’s entering your aquarium, while increasing the amount of DOC’s exiting your aquarium. Remember there is no quick fix for Cyanobacteria. Thank you for reading about How to Control Red Slime Algae and Cyanobacteria.