There are plenty of reasons to install a planted refugium into your reef aquarium system. You might culture macroalgae for numerous purposes including removing excess nutrients, growing a live food for herbivores, creating pod microhabitat, or just for simple enjoyment. Some macros are better suited for some of these purposes than for others. Therefore, if you keep a planted ‘fuge for multiple uses, then it may be best to use some combination of macroalgal species (mixed macros!).
We here present a few possibilities for macroalgal “multi-tasking.” This is by no means the extent to which you can incorporate several species in your marine garden to best accomplish a particular goal. For example, in some cases, you might choose to utilize three or four species. You might even fine tune your crop by finding the ideal proportional size of each species in the garden. You might add and/or remove different species as current conditions in the tank demand. And so on!
The nutrient sponge
Both chaeto (Chaetomorpha linum) and sea lettuce (Ulva lactuca) are known to be very fast growers and, therefore, excellent choices of macro for nutrient sequestration. Of course, both of these are chlorophytes (e.g. green algae) and therefore require intense lighting; unless they receive the powerful light energy required for fast growth, they will grow much more slowly or even die off. Simple as that!
If grown under a strong light (such as the Kessil H160 Refugium Light), both chaeto and sea lettuce thrive. Sea lettuce in particular can grow at spectacularly high rates, especially in nutrient-rich environments.
This particular combo allows for maximal nutrient removal in eutrophic (i.e. high-nutrient) environments. Specifically, the sea lettuce can respond quickly and intensely to elevated concentrations of nitrate and phosphate, proliferating rapidly. However, the presence of the loose, wiry chaeto in the bed helps to keep the soft, fan-shaped blades of sea lettuce from packing against each other and/or the outlet drains. It also allows for overall higher rates of water flow, which increases for higher turnover through the ‘fuge and potentially more efficient nutrient sequestration.
As it happens, the physical environment this creates makes an excellent habitat for harpacticoid copepods and other small benthic microcrustaceans!
The mixed salad
Especially where dissolved nutrient levels are near desired levels, and the tank houses obligately herbivorous fishes and inverts such tangs, large angelfish, batfish, rabbitfish, sea urchins, certain crab species, etc., it is advantageous to grow edible macros. The best types for this purpose are not only wholesome and devoid of allelopathic (i.e. noxious or toxic) compounds but are also soft (i.e. easy to chew to swallow). Some of the most nutritious and delicious soft macros are sea lettuce and red ogo (Gracilaria parvispora).
Sea lettuce and red ogo are both fairly easy to grow. Also, they are both relatively simple to harvest, as they grow in small clumps that can effortlessly be picked from the algal mass for use as a high-quality live food for larger herbivores. Clumps can be dropped right into the tank (some large fishes, for instance, can suck them up as is) or attached to an algae clip.
The great thing with this set of mixed macros (being as Ulva is a chlorophyte and Gracilaria is a rhodophyte (red algae)) is that each of the two species has its own nutritional benefits. So, used together, they present a more varied diet. For example, sea lettuce is a great source of vitamins from group B (e.g. cobalamin and vitamin B12) whereas ogo is a great source of iodine and bromine. Each boasts its own distinct set of healthful carotenoids.
Sure, herbivores can be incredibly finicky about their foods. If you find that most of your herbivores prefer one type, you can offer the other type first–while they’re most hungry and most likely to accept the unfavored alternative. This practice helps to ensure that all herbivores are enjoying a reasonably balanced diet.
Easy on the eyes
Hobbyists who have gained good control over their water quality can relax a bit and enjoy the more ornamental varieties of macroalgae. Those with low-to-moderate nutrient levels and intense refugium lighting have the enviable option of cultivating some of the most beautiful seaweeds such as dragon’s breath (Halymenia dilitata) and blue hypnea (Hypnea pannosa). Such is a ‘fuge worthy of showing off alongside the main tank!
When displaying ornamental mixed macros, any number of species will do. But the more the merrier! This is especially so when species are selected to complement each other’s shapes and colors. Take for example dragon’s breath and blue hypnea. The former is velvety red and leafy, while the latter is iridescent blue and lacy. When set closely beside each other, each stands out even more boldly and beautifully.
Both species naturally inhabit rocky subtidal environments (with Hypnea preferring slightly shallower waters than Halymenia). Since Hypnea requires slightly stronger light, one could build a rubbly refugium bottom, with Hypnea at the tops of the rocks and Halymenia between them on the bottom. The dash of green provided by a mangrove might make the display even more visually pleasing!
Mixed reasons for mixed macros
Again, the above suggestions present just a few of many, many possible examples of ways aquarists can make good use out of mixed macroalgal beds. With a decent understanding of the basic requirements and benefits of each macro species, anyone can build a planted refugium and sea garden that suits their own unique needs!