How Fast Does Macroalgae Grow?

A good portion of hobbyists will grow macroalgae in their reef tank systems. It has even become more common to see planted display tanks in recent years. Algae scrubbers and refugia are also very popular and effective ways to export wastes in the reef tank. Since many of the fish and invertebrates we keep in the hobby are herbivores, having a supply of fresh macroalgae is very convenient. Many hobbyists have found that growing macros as a food source is easy. And as a bonus, growing macros can control nutrient levels in the reef tank!

Several macroalgae species are very beneficial in reef tank systems. In addition to supplying food for herbivores they also reduce phosphate and nitrate levels. Copepods, a staple meal for certain fish and invertebrates kept in reef tanks, breed happily in systems with macro. In this article, we will briefly touch on what influences strong growth rates in macros.

What Exactly is Macroalgae?

Macroalgae are algae, which is a large category of aquatic plants. Algae (primary producers) include single-celled phytoplankton and multi-celled macroalgae, or seaweeds. These range in size from microscopic to large. Seagrasses should not be confused with macroalgae. This is because seagrasses have roots and vascular tissue. They even produce blooms and pollen. So, they are more closely related to terrestrial plants. On the other hand, macros have holdfasts rather than roots. The holdfasts serve only to physically anchor them to substrate.

Types of Macroalgae

There are over 10,000 different types of macroalgae! They are divided groups based on their color. There are three main types of macros. There are green algae, which include sea lettuce. Then, there are brown algae, which include large kelps. Red algae are the most diverse group of all. Different photosynthetic pigments or chlorophylls used by each alga reflect different wavelengths of light. This results in the various colors of algae.

Where to Find Macroalgae?

Macroalgae are purely benthic plants. They will be linked to the substrate or a solid objects like rocks, mangrove roots, boat hulls, jetty pilings, or mooring lines. Most macros have a short lifespan as free-floating seaweed drifts when dislodged. They can live anywhere from a few hours to several months.

Only a tiny amount of macroalgae, such as Caulerpa species, may grow on soft sediments. Caulerpa will anchor itself with long root-like rhizoids or by entangling around seagrass fronds. Macroalgae grow intertidally and subtidally. Because macroalgae are photosynthetic creatures, they can only grow in the “photic” zone of coastal areas. A photic zone is where enough light enters to allow photosynthesis.

Growing Macroalgae

To thrive, most macros need medium to intense light. The color of the macros can change depending on the strength of the light. Macro can modify the pH of the water through respiration. Therefore, water parameters should be monitored closely for major swings. However, this can be used to stabilize the pH of the system. Using a refugium timer set to an opposing schedule can help to avoid dramatic pH swings.

AlgaeBarn has great varieties of macroalgae for beginners. Sea Lettuce is a low-maintenance green macro that can withstand some parameter fluctuation. Chaetomorpha is another great choice for newer reef keepers. This macro variety does require more intense lighting. If harvested regularly, chaeto is excellent for filtering out excess nutrients from the water. To attach a mat of macroalgae, simply attach the holdfast to a piece of rock or a shell. Super glue or epoxy can be used if necessary.

Keeping Macroalgae in the Reef Tank

If there is difficulty getting macroalgae to thrive, one of the elements is most likely limiting growth. Appropriate levels of micronutrients are crucial for healthy macroalgae growth! Iron, iodine, phosphate, and nitrate are all essential for growth.

One of the more pressing issues with macros is that they can quickly exhaust nutrients from the water column.

Macro can grow very quickly and then suddenly growth will slow. In some cases, the macro will begin to die off. This is a clear sign that they have exhausted certain elements and need supplementation. It is critical to monitor for this and dose trace elements when needed.

Water Quality

The ideal water conditions for growing macroalgae are not difficult to achieve for a reef keeper. The salinity should be kept between 1.024 and 1.026. While some macro species can handle large salinity swings, others may not. The optimal temperature range for keeping macroalgae is between 75 – 79 °F (24 – 26 °C). Although species such as Sea Lettuce can withstand higher temperatures. It may be necessary to dose modest amounts of nitrate and phosphate to the reef tank system. Some species of macro are so efficient at waste export and may actually strip the water column of these essential nutrients.

Some Advantages of Growing Macroalgae

Macro will naturally remove nutrients from the reef tank. They will compete with nuisance algae and improve overall water quality. Sea lettuce is an excellent choice for removing excess nutrients and doubles as a food source for copepods! Many species provide safe havens for beneficial inverts such as copepods. Macros can provide fish with the natural cover they seek and encourage their natural behaviors. Many seahorse species, for example, rely on macroalgae and seagrasses to survive.

Macros do need adequate lighting but sometimes less than what corals demand. Most macroalgae can thrive in a tank with lower lighting. Macro species such as Red Pom Pom are a beautiful addition to a reef tank system. The bright burgundy coloration can be just as striking as coral in the main display tank. Many macros are even more fascinating than coral! Also, they can better withstand temperature and environmental swings, making them great for newer reef keepers.

Conclusion

Corals aren’t the only way to build a beautiful reef tank. Macros are an excellent way to add exciting colors and textures to the reef tank system. And there is the benefit of having fresh food for hungry herbivores. One of the simplest things we can do to assist in natural filtration is to grow macro! There are many different types of macroalgae to choose from so it is simple to find the variety that will do best in every reef tank. AlgaeBarn offers several varieties of macros, and all are sustainably grown. This article should help to clear up any questions on what affects the growth rates of macroalgae.