To effectively remove brown algae, commonly known as diatoms, from your reef tank, you need a combination of manual removal and addressing the underlying cause, primarily excess nutrients like phosphates and silicates. A direct method involves starting the siphon and then as you brush and dislodge it the brown algae gets sucked up and removed.
Brown algae often appears as a dusty, brownish film on glass, substrate, rocks, and equipment shortly after setting up a new tank, or in mature tanks when nutrient levels are elevated. While diatoms are a natural part of a tank's cycle, excessive growth indicates an imbalance.
Manual Removal Techniques
Physically removing the algae is the first step to improve the tank's appearance and reduce the biomass contributing to nutrient cycling.
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Siphoning While Brushing: This is one of the most effective methods for removing diatoms from surfaces like substrate and rockwork.
- Take a siphon hose connected to a bucket.
- Position the open end of the siphon close to the area you are cleaning.
- Use a brush, toothbrush, or algae scraper to gently dislodge the brown algae.
- As the algae lifts off the surface, the siphon immediately sucks it up into the waste bucket.
- This prevents the dislodged algae from simply settling elsewhere in the tank and continuing to decompose.
- As highlighted in the reference, you may need to repeat this process daily if necessary, especially in conjunction with efforts to lower nutrient levels.
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Glass Cleaning: For glass or acrylic surfaces, use appropriate algae scrapers or magnetic cleaners. Wipe or scrape the algae downwards into an area where you can easily siphon it out or where your filtration can capture it.
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Substrate Cleaning: Use the siphon directly over the sand bed or substrate, gently stirring the top layer to lift diatoms and detritus for removal.
Addressing the Root Cause: Nutrient Control
Manual removal provides temporary relief, but the algae will return if the underlying nutrient issues are not fixed. Diatoms primarily feed on silicates and phosphates.
Identifying and Reducing Nutrient Sources
High levels of phosphates and silicates are the main drivers of diatom blooms. These can come from:
- Tap Water: Tap water often contains phosphates and silicates. Always use RODI (Reverse Osmosis De-Ionized) water for top-offs and water changes. Ensure your RODI unit's filters and DI resin are fresh.
- Food: Overfeeding or using low-quality foods can introduce excess nutrients. Feed sparingly and use high-quality, nutrient-dense foods.
- Source Rock/Sand: Some dry rock or sand may contain bound phosphates that leach into the water.
- Dead Spots: Areas with low flow can accumulate detritus, which breaks down and releases nutrients. Ensure adequate flow throughout the tank.
Nutrient Export Strategies
Actively removing nutrients from the water column is crucial for long-term control.
- Water Changes: Regular water changes using RODI water help dilute nutrient concentrations.
- Filter Media: Utilize filter media designed to adsorb phosphates and silicates.
- Granular Ferric Oxide (GFO): Effective at removing phosphates.
- PhosGuard: Removes both phosphates and silicates.
- Use these media passively in a media bag in a high-flow area or actively in a media reactor for best results. Follow product instructions and replace media regularly.
- Protein Skimming: A good protein skimmer removes organic waste before it breaks down into phosphates. Ensure your skimmer is properly sized and maintained.
- Macroalgae Refugium: Growing macroalgae (like Chaetomorpha) in a separate sump section (refugium) consumes nutrients like phosphates and nitrates. Periodically harvesting the macroalgae exports these nutrients from the system.
Effective phosphate removal is key, as stated in the reference. Gradually, as phosphate levels decline through consistent manual removal and nutrient export, the regrowth should become less and less.
Prevention and Long-Term Control
Maintaining low nutrient levels and a healthy tank environment is the best defense against future diatom outbreaks.
- Optimize Lighting: While not the primary cause of diatoms (which are less light-dependent than green algae), controlling light duration and intensity can help manage overall algae growth. Aim for a reasonable photoperiod (e.g., 8-10 hours).
- Cleanup Crew: Introduce a diverse cleanup crew that includes species known to graze on diatoms.
- Snails: Trochus, Nerite, Cerith, and Astrea snails are excellent diatom grazers.
- Hermit Crabs: Some hermit crabs may graze on diatoms, but be cautious as they can sometimes bother other tank inhabitants.
- Maintain Good Flow: Ensure sufficient water flow to prevent detritus from settling and to keep diatoms from coating surfaces easily.
By combining consistent manual removal with rigorous nutrient control and good husbandry practices, you can effectively eliminate brown algae and maintain a clean, healthy reef tank.
