MACROALGAE LIGHTING
WHAT LIGHTING SHOULD YOU HAVE FOR GROWING MACROALGAE?
Correct lighting is one of the fundamental aspects of growing macroalgae correctly, many people grow macroalgae in a sump refugium with an incorrect spectrum or power of light due to wanting to cut costs and the belief that macroalgaes require minimal lighting to grow successfully. Although some macroalgaes such as chaetomorpha
can grow in very poorly lit conditions, this is far from ideal. In a sump refugium the idea is normally to grow the macroalgae as well as possible to promote the uptake of waste materials from the water column, it is therefore counter productive to only provide the macroalgae with the bare minimum of light for survival.
When growing macroalgae in your main display aquarium as the prominent feature or mixed in amongst a full reef tank including corals, generally the modern types of lights designed for corals will be ideal for growing macroalgae as well, however there are some aspects of lighting you may want to consider if the tank is mainly for growing macroalgaes with minimal to no corals.
Lighting type fluorescent bulb or LED?
In the modern day LED lights have completely revolutionized the lighting available for aquarium use. Almost all aquariums made now, at least not at the extreme budget end, will have some type of LED lighting. There are a few reasons for this such as lower electricity costs due to LED lights using a fraction of the wattage compared to fluorescent bulbs and tubes, but also the fact that LED's can be "Tuned" to specific wavelengths so that they can hit the parts of the visible light spectrum that allows plants and corals to grow. In comparison, old style fluorescent lighting is more of a general full spectrum light which hits the correct spectrum for plants and corals but also has a lot of left over light in parts of the spectrum not needed by the corals and plants to grow, which is wasted light energy and can help promote unwanted algae. That being said some fluorescent lights are "tuned" by the specific mix of gases inside to give out certain kelvin of light, such as marine actinic bulbs and plant spectrum bulbs etc, but they still will never have as specific a spectrum as an LED light.
Fluorescent bulbs also have a relatively short life span due to gas degradation within the bulb, which leads to deterioration of the light spectrum quality the bulb produces, this means they have to be replaced every 1-2 years to maintain the correct spectrum for the macroalgae or corals. LED lights tend to have a life span of ~50,000 hours and the spectrum will change very minimally within this time, making them much more stable light output compared to fluorescent lights, and stability is key in saltwater tanks.
One thing to note about LED lights is that there are a massive variety of LED's on the market and they can be VERY different in terms of quality. High end aquarium lighting may use CREE LED's, as these are high quality LED's with exceptional lumen / PAR output and will be tuned specifically for a reef or planted tanks' inhabitants. Conversely other lights, normally the "budget" lights, may be made from generic white/colored LED's which may lack in lumen output and also may not be tuned as tightly or at all to the spectrum you require. This means it's very important to look at the quality of the LED's in the light you're buying to make sure they are of a good quality, output the correct spectrum and have good lumen / PAR values.
To answer the question, I would recommend good quality plant or reef spectrum tuned LED lights over fluorescent bulbs / tubes for growing macroalgae.
What colour spectrum for macroalgae?
Macroalgae have very similar needs in terms of light spectrum to terrestrial plants. There are some noteworthy differences however and these can be easily identified by the colour of the macroalgae themselves. There are three groups of macroalgae which is determined by their pigmentation; green macroalgae (chlorophyta), red macroalgae (rhodophyta) and brown macroalgae (phaeophyceae). The colouration of the algae is related to the depths they live at and gives us a huge hint to their lighting requirements.
Green macroalgae tends to live in shallower waters and uses a similar spectrum of light as terrestrial plants, reflecting green light away and using blue/red spectrum at certain chlorophyll peaks. Because of how similar they are in terms of light requirements to terrestrial plants, it's easy to predict that they will grow under a variety of lighting. Green macroalgae do especially well under full spectrum 6500K lighting because this is a full sunlight spectrum; but also green macroalgae in general will do well under reef spectrum lighting in the higher 10-12,000K range. This is why they can survive so well when abused in a refugium environment with dull or incorrect lights.
Red and brown macroalgae live deeper in the reef environment, browns being the deepest inhabitants. Due to this, just like corals, they rely on a diminished light spectrum. Although there is a huge variety of red and brown macroalgae all specifically evolved for their environment, in general they rely more on the blue spectrum of light, with some reliance of accessory pigments using the green spectrum in some species.
How long to leave them on?
There is some debate around the length of time a macroalgaes photo period should be. Green macroalgae tends to like a longer photo period of around 10-14 hours, and some people have a 24hr photo period for chaetomorpha and some caulerpas as it seems to promote faster growth and reduction of caulerpa "going sexual" and melting away. Green macroalgae seems to tolerate longer photo periods and even some species seem to thrive under these conditions, however it can cause problems such as high nutrient usage leading to deficiencies and quickly dying off in a "boom and bust" way if not provided enough fertilizers.
Red and brown macroalgae will not tolerate intense lighting for such long photo periods and I recommend a standard photo period of around 8-12 hours, very much like a freshwater planted tank. If over exposed to light for too long, or it's too bright, red macroalgae can bleach, losing colour and whiting out. This can cause the red macroalgae to die, however quickly identifying and rectifying the problem (reducing light intensity / photo period) can save macroalgae affected in this way.
In general, if doing a mixed macroalgae tank of green/red and brown macroalgaes I would recommend a photo period of between 8-12 hours.
My TOP
Picks For Refugium Macroalgae Lights
hygger Clip On Full Spectrum Aquarium Light
The hygger clip-on light is designed for various planted tanks ranging from 11 to 55 inches long. It features an easy-to-install clip-style bracket, making it suitable for standard-rimmed aquariums. In addition to full spectrum lighting, it includes a Day-Night dual timer with Sunrise-Day and Sunset-Moon settings, adjustable with 9 color options for planted tanks. The thick aluminum construction enhances heat dissipation efficiency, and the detachable adapter allows easy replacement without needing to replace the entire light if it becomes damaged
IREENUO LED Aquarium Light, Full Spectrum Clip on Light with Remote
Correct spectrum for macroaglae growth and comes with 24-hour Automatic Sunlight Cycle Mode. You can also choose the custom color mode to create a lighting solution tailored to your aquatic plants.
Adjustable clip on fish tank light, which can be clamped on any position of the fish tank wall whose maximum thickness is 0.9 inches (2.3 cm).
Low power consumption operation promises the security of aquarium lighting. Energy-saving LED light allows low power consumption even for a long time working.
