How to Avoid Going Green in the Reef Aquarium
Before I start, please understand that I am not suggesting aquarium keepers should avoid making their setups more energy efficient or lessen their ecological impact on wild reefs and fish populations. In fact, "going green" in the aquarium trade is a very desirable goal for any hobbyist, as it has both self-serving and selfless benefits, such as a reduction in energy bills and relieving the stresses on the environment. What I am talking about instead, are green pigmented corals. Despite being very beautiful in most instances, adding too many green corals, or any other color for that matter, to one reef aquarium can really take away from the visual appeal. Due to their overabundance unfortunately, green corals dominate the aquarium trade. In addition to being prevalent at most fish stores, the green scene may not be as avoidable as one might think considering the aggressive behaviors of some coral types and the ability of many corals to morph under different lighting. Fortunately for aquarium keepers, there are ways around such reef-related pitfalls.
Green corals show up in the many different Zoanthid and Palythoa morphs, as countless SPS and LPS corals, and even in non-photosynthetic corals to a lesser extent. Because the color is so common, corals of this hue are readily available to collectors and wholesalers, and they often flood local fish stores and eventually the home aquariums. The typical new reef tank often starts off with a few green corals here and there, but eventually becomes swamped as the appetite for more livestock takes hold and a steady supply of green corals fills local fish stores. The limited selection forces the aquarist to make poor coral purchases, and the tank’s overall appearance suffers because of it.
Australian Acans are very beautiful and were once very popular. Most sought after Acans had multiple colors, but this particular coral is almost completely green.
Preventing a reef from becoming overrun with green may seem as simple as avoiding the purchasing of large amounts of green livestock. Unfortunately, it isn’t quite that simple. Taking the preventative route is certainly a great place to start, but aquarium keepers also have to consider how fast the green corals in their aquariums grow and how they affect the growth rates of other corals that share the same living space. In terms of growth, a green coral doesn’t necessarily grow more quickly in the home reef aquarium than corals of a different color. Instead, growth rates are dependent on a myriad of water parameters and available aquarium equipment. Despite the relatively uniform conditions in an aquarium, some species grow far faster than others. For example, the green star polyp coral (Pachyclavularia sp.) grows like a weed under virtually every type of aquarium lighting and under a wide variety of water conditions. Eventually, their vibrant neon green polyps can be spotted all over the rocks and even on the aquarium itself.
Even though the Green Star Polyps have a purple base, the fluorescing green polyps grow very tightly backed together, making the entire coral appear neon green.
Besides growth rates of the green corals, the aquarist must also understand how the growth rates of other corals in the tank can be impacted. The green Galaxy coral (Galaxea sp.), a calcifying hard coral that grows fairly quickly, will send out sweeper tentacles to sting anything and everything within reach. This territorial behavior will not only halt the victim coral's growth in that particular direction, but it may also stress it to the point of bleaching or even total colony death. Additionally, many soft corals release metabolic byproducts that inhibit the growth of hard corals from the genus Acropora. While the impact of these growth inhibitors may not be extensive, it can certainly help a tank become dominated by only a handful of green individuals.
The green Galaxea coral can send out long sweeper tentacles to sting any nearby corals, causing tissue damage and even bleaching.
Another cause for concern for the aesthetically aware reef keeper is coral color morphing. When hobbyists see images of corals online or even the real thing at a local fish store, chances are the coral will look different in their aquarium. The differences may only be subtle and may take months to develop, but they can also be quite drastic and occur almost over night. Sometimes the color morph can be for the positive, as ugly corals have been seen turning into gems under the right conditions. Unfortunately though, the morphing corals typically “brown out” or completely change from one color to another. The reason for color change in corals is primarily due to water quality and light spectrum differences between the store’s aquarium and that of the reef hobbyist. Many stores use heavy actinic lighting to make their corals appear more fluorescent, but most aquarium hobbyists use a more natural looking white light with only some actinic supplementation. Blue, yellow, and even red corals have been known to turn green over time, making formerly beautiful coral fade away into the crowd of green.
Having a single dominant color in any reef tank can really take away from the visual appeal of the aquarium. The tank may have a gorgeous live rock layout and beautiful fish, but by not diversifying the colors, any great looking tank can turn into a very boring one. With all this in mind, I wanted to reiterate that green corals aren't inherently bad because of their color. They can be very attractive on multiple levels, and for certain coral species the color is very rare. Unfortunately, because the color is just so common, it is typically looked down upon and is often the scapegoat of negative conversations regarding aquarium aesthetics. Despite this, I will continue to use a little greenery in my aquariums, while also trying to avoid purchasing too many greens and instead focus on the red, blue, orange, and purple colored corals whenever possible.