Saltwater Aquarium Algae & Algae Management | How to Identify Brown Algae, Cyanobacteria, and Dinoflagellates

Introduction: Why Do Algae and Coking Occur?

When operating a saltwater aquarium, many people experience at least once the brownish film-like deposits, greenish or reddish-purple slimy film, or grayish to brownish powdery deposits. These are commonly referred to collectively as "algae," but in reality they contain biologically completely different groups mixed together. Even if they look similar, the treatment methods vary greatly depending on the type, so the first step in countermeasures is to identify "what is occurring."

In newly set-up tanks, biological filtration is not yet stable, and the balance of trace elements and nutrients is easily disrupted, so temporary algae outbreaks are not uncommon. If seen during the tank cycling and setup process, many cases settle down over time. Conversely, if they suddenly increase months after the tank is established, changes in daily management habits such as increased feeding or reduced water change frequency may often be the trigger. First, reviewing what has changed recently (lighting duration, feeding amount, additive amounts, addition of new livestock, etc.) will help narrow down the cause.

Characteristics and Treatment of Brown Algae (Diatoms)

So-called "brown algae" is in many cases a single-celled alga called a diatom. It forms a thin brownish film on glass surfaces and sand, and has the characteristic of becoming powdery when wiped. Since diatoms use silica (silicic acid) as their shell material, they become prone to occurrence when silica derived from tap water is introduced.

Basic treatment is as follows.

• Clean glass surfaces and perform regular water changes to remove silica and nutrients
• Use RO/DI water purifier to reduce silica and phosphate from tap water
• Have them eaten by cleanup crew such as snails and hermit crabs

Early-stage diatoms in newly set-up tanks are often temporary and tend to decrease naturally as the tank matures. Rather than hastily relying on chemical treatments, the basic approach is to continue methodical water changes and physical removal by cleanup crew while waiting for the tank's biological filtration to develop.

About Green Algae (Hair Algae and Ulva Species)

Green filamentous or hair-like algae and thin green sheet-like spreading ulva species are also commonly seen algae in saltwater aquariums. Compared to diatoms and cyanobacteria, they are less likely to carry toxicity or foul odors, and are often treated as aesthetic issues, but if left unattended can obstruct water flow or cover coral surfaces. Basic treatment is common with other algae types, focusing on suppressing excess nutrients, feeding by cleanup crew, and careful removal.

Characteristics and Treatment of Cyanobacteria (Blue-Green Algae)

Reddish-purple to dark green slimy sheet-like deposits are often "cyanobacteria," a type of bacteria distinct from diatoms (also called blue-green algae). When peeled away, it comes off as a thin film and often has a distinctive odor. Strictly speaking, it is not algae but a photosynthetic bacterium, but it is conventionally treated as a type of "algae."

Cyanobacteria are said to proliferate easily in areas where water flow is stagnant or in environments where phosphate and nitrate levels are consistently high. Countermeasures include the following.

• Review water flow pumps and reduce dead spots (areas where water stagnates)
• Review protein skimmer capability to export organic matter early out of the system
• Stably export phosphate and nitrate using refugiums and similar methods
• Physically siphon out and remove, and clean up the accumulation areas of organic matter (detritus deposits) that serve as sources of recurrence

Dinoflagellates: Characteristics and Precautions

"Dinoflagellates" is a general term for single-celled organisms called dinoflagellates, and in saltwater aquariums they are often confused with brown algae and cyanobacteria. They can spread on sand surfaces, rocks, and coral surfaces as brownish to yellowish-brown slimy material accompanied by bubbles, and the presence of bubble-like particles visible when light is applied is considered a clue for identification.

Dinoflagellates are said to be more difficult to treat than other algae, and cases where improvement is not seen with just general water changes and nutrient management have been reported. It is sometimes said that reducing nutrients to extreme levels actually increases their vigor, which differs from the treatment approach for cyanobacteria and diatoms, highlighting the importance of proper identification. If the area spreads or impact on corals and livestock is suspected, consider consulting a specialized aquarium shop or experienced keeper rather than making strong medication decisions or causing rapid environmental changes based on personal judgment.

Tank-wide Preventive Approach

Algae countermeasures are said to be more effective when maintaining an environment where occurrence is prevented from the start, rather than individually tackling problems after they occur. Developing the habit of the following basic management practices will serve as a foundation for prevention against any type of outbreak.

• Keep feeding amounts matched to the number and size of livestock, and do not leave uneaten food sitting for long periods
• Perform regular water changes to reset the accumulation of phosphate, nitrate, silica, and other substances
• Based on basics of water chemistry, regularly measure parameters to understand trends
• Do not make lighting duration excessively long, and maintain consistent photoperiod
• When introducing new livestock or layout materials, be careful not to introduce organic matter from unknown sources

Key Points for Identification and Common Prevention Strategies

Rough clues for distinguishing three types are as follows.

What is commonly important regardless is stable nutrient balance and appropriate water flow and filtration capacity. Rather than taking drastic action, taking a methodical approach to sorting out the cause and improving the environment will lead to prevention of recurrence. If improvement is not seen or you are uncertain in your judgment, it is recommended to consult a specialist shop before relying on self-directed overuse of medications.