If you’ve decided to install a refugium in your reef aquarium system, you may have just made the best decision you’ll ever make as an aquarist. But now you have another important decision to make: What kind of macroalgae to keep in it?
Which macro--or macros--you should cultivate depends upon the primary purpose you expect the refugium to serve.
Do you mainly want to remove excess nutrients from the water? Then you will want fast growers. These generally are green algae (chlorophytes). And just so you know: Fast growth requires high rates of photosynthetic production, which requires very intense lighting! The two most popular green algae used for nutrient sequestration are quite different from one another. The first, Chaetomorpha, is stiff and wiry, and therefore can withstand high rates of flow. This makes it most suitable (and efficient) for smaller refugia or algae reactors. Ulva, the second type, is also quite productive; however, because of its leafier structure, it is more prone to self-shading and therefore grows in comparatively shallower beds. Thus, in order to achieve the same rate of sequestration under the same lighting, it requires a bit more space. Still, Ulva is a fantastic choice, as its soft, leafy fronds are greedily eaten by many herbivorous fish and invertebrates, which brings us to another consideration.
Do you mainly want to grow a live “vegetable” food for animals such as angelfishes, tangs, boxfishes, etc.? Then palatability is key. In addition to Ulva, soft red algae (rhodophytes) such as Gracilaria (especially the “ogos”) are great choices. Because red algae are not as particular about lighting, they are the better choice if you are not using a plant-specific, high-intensity lighting system. Just know that you’ll have to be even more on top of replenishing trace elements such as iodine!
Do you mainly want to have a mixed crop for ornamental purposes? Who could blame you; macroalgae are beautiful and are interesting to cultivate! In fact, marine gardening is fast becoming a major interest amongst saltwater aquarists. Just know that this is more challenging than one might think; for a mixed bed, you’ll need to opt for the best and brightest lighting, regularly add trace elements and prune quite regularly. The reward, of course, is a lush and gorgeous display!
The best thing about a refugium, in the end, is that you can add/switch types of macros as your needs change!
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