Chaetomorpha: A Classic Macroalgae Favorite - Function, Care and Troubleshooting

Growing macroalgae in an aquarium refugium has long been recognized as a natural and highly effective way to support water quality and overall system health. Among the different types of macroalgae, Chaetomorpha, commonly known as chaeto, stands out as one of the most popular choices. It helps remove excess nutrients, contributes to gas exchange, provides a safe habitat for copepods and other microfauna, and improves water clarity. While chaeto is not typically grown for aesthetics, its success in a refugium directly reflects how well it is performing these valuable functions.

The primary goal of keeping chaeto is to encourage steady growth. When it thrives, it is actively consuming nitrates and phosphates, creating a natural form of nutrient export. Healthy, growing chaeto also generates surface area where beneficial microfauna can flourish, contributing to a more balanced and self-sustaining ecosystem. However, when chaeto becomes brittle, pale, or begins to break apart, it signals that conditions in the system may not be meeting its needs.

At the most basic level, chaeto requires adequate light and nutrients. While most reef systems already contain enough nutrients to support macroalgae growth, lighting can vary widely. Algae tends to respond best to light rich in the red spectrum, so choosing a refugium-specific light often leads to stronger growth than relying on standard aquarium lighting. Without sufficient intensity and spectrum, even nutrient-rich systems may see chaeto struggle.

Nutrient balance can present a different kind of challenge. In tanks where nuisance algae is present, microalgae in the display often consumes nutrients as quickly as they become available, leaving chaeto with little access to fuel its growth. Physically removing nuisance algae can shift the balance in favor of macroalgae. In some very low-nutrient systems, particularly in mature aquariums, it may even be necessary to increase feeding or dose a fertilizer to support sustained chaeto growth.

Beyond light and nutrients, other factors can influence chaeto health. Adequate water flow is essential, as stagnant areas inside the mass of algae can cause die-off. Most sump designs provide sufficient circulation, but if growth becomes compacted or sluggish, adding an air stone or additional flow can help keep water moving through the ball. Stability in salinity also plays a key role, as sudden fluctuations can stress macroalgae just as they stress corals and fish. Using an auto-top-off system helps maintain consistency, but it’s best to add freshwater to a section of the sump that does not house the chaeto directly.

Just as important as providing the right conditions is harvesting chaeto regularly. Left unchecked, it can grow so densely that inner portions receive little light or flow, leading to decay.

Keeping chaeto healthy is not difficult, but it does require some attention to the fundamentals. When cared for properly, it becomes more than just a filter, it transforms the refugium into a dynamic, living system that supports the broader aquarium. A thriving ball of chaeto turning gently in the water is more than just a pleasant sight; it is a sign of balance, stability, and long-term success in the marine aquarium.

 

 

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