A sea turtle gently hovers over a ridge close to shore. On the ridge beneath the turtle are dozens of coral colonies: stony domes, thick branches, pulsing flowers, waving bushes, and solid plates. And within and around this colorful forest swim hundreds of little fish. Eels pop their heads out of holes, sea stars grasp at food, sharks patrol the area, and cleaner shrimp pamper their customers.1
As a functioning replica of the coral reef ecosystem that the sea turtle cruised over, a reef aquarium system offers a unique opportunity to experience and observe the workings of coral reefs. One aquarium is not, admittedly, a large sample of coral reefs around the world, but it still offers an in-depth look at a small section of reef. And there are many things to learn indeed from this small-scale replica.
The Science behind the Reef Aquarium
While a reef aquarium is not the real thing, the artificial reef shares many important characteristics with the wild coral reef. Most importantly, the organisms in both artificial and natural reefs, especially fish and invertebrates, can only thrive within a small range of water parameters such as salinity, pH, temperature. Also of significance, many of the same biological processes found in nature happen in the aquarium.
What is a coral reef?
First, to understand a coral reef you must know the basics of a coral. Most importantly, corals are living animals, and what most people think of as one coral is actually not a single animal but the quality the colony of hundreds of individual coral polyps. Each polyp is like an upside down jellyfish, with a mouth and tentacles. In stony corals these individuals secrete a limestone skeleton to support and connect the colony.
The brilliant colors of corals come from “photosynthetic algae, called zooxanthellae, that live in their tissues.2” The algae and polyps live in symbiosis, where the algae provide energy and oxygen in exchange for protection in the corals. Due to this relationship, corals often seem like plants because they obtain most of their nutrition from photosynthesis, but corals are still animals as they can eat.3
Stony corals, with their rock-like skeletons, form a diverse ecosystem. A quarter of all marine organisms, estimated at around 2 million species, depend on this coral jungle an, which takes up less than 1% of the ocean. The plethora of life in a typical coral reef includes stony and soft corals, giant clams, various shrimps and crabs, multitudes of tropical fish (angelfish, damselfish, clownfish, tangs, eels, and etc.), octopuses and squids, sea turtles, sea cucumbers, and sea stars. In fact, coral reefs are as rich in life as the Amazon rain forest.4
All of this life is supported by bacteria and other microorganisms living in the coral “rock” and sand holding the reef together. These detritivores and decomposers keep the reef free of extra waste and nutrients. This process of breaking down animal waste, dead organisms, and nutrient ands is called biological filtration.
Biological filtration, in both aquariums and the ocean, begins with scavengers like hermit crabs and sea cucumbers eating fecal and dead matter. Next, the rotting flesh and scavenger waste releases toxic ammonia, which bacteria then process into harmless nitrogen gas.
The reef aquarium as a replica of the wild reef
A reef aquarist’s job is to provide a suitable space for corals to grow and fish to thrive. The reef-keeper must also ensure the health and survival of scavengers and microbes. All of this life flourishes in a reef aquarium only if the aquarist provides some fundamental equipment and supplies such as the aquarium itself, a filtering device to remove part of the waste, lights, heater, salt, filtered water, and live rock on which beneficial bacteria live. The above-named equipment serves to maintain the perfect water quality and conditions reef organisms need.
So, keeping a reef system becomes a challenge of maintaining pristine water conditions. The right water means filtered water mixed with special salt at an exact salinity and heated to a temperature between 75 and 82 degrees Farenheit, and clean water means saltwater low in nutrients and waste. But at the same time that nutrient levels need to be very low, the fish must have enough food to be healthy. Leftover food and fish waste both are primary producers of nutrients.
There is a paradox here. One one hand, you have to feed the fish, but on the other hand feeding pollutes the water. The needs of the fish and corals are ever-competing.
What does a reef aquarium teach?
While the wonders of the coral reef can be learned through Internet searches and books, a reef aquarium gives everyone a chance to experience a coral reef with their own eyes. Not everyone can fly to Australia or the Bahamas. And even if everyone could explore natural reefs, such an influx of humans would do more harm than good.
Having more people experience coral reefs through aquariums means a more urgent desire to protect coral reefs around the world. Coral reefs are worth conserving because of the diversity and volume of life contained in them and the economic and environmental benefits to people.
According to the Queensland Museum in Australia, coral reefs benefit humans by protecting coastlines from damaging waves and storms and providing fish for the fishing industry.5 In other words, coral reefs protect the land that we live on and supply the food on our tables.
Furthermore, knowing that a coral reef ecosystem needs just the right conditions and experiencing some ways of maintaining those conditions makes people more aware of what needs to be done protect this valuable marine resource. And coral reefs definitely need protection. Today’s coral reefs are threatened by carbon dioxide pollution (increased CO2 in the ocean impedes the ability of corals and other reef invertebrates), agricultural and industrial runoff (water pollution “dirties” coral reefs, causing non-symbiotic algae to overgrow the corals), “destructive fishing methods,” “coastal development,” and “the global aquarium trade”6.
Now, the last threat listed seems to undermine my entire argument. But the aquarium trade is only a threat if aquarists continue to buy wild caught specimens–I have to admit that, at times, I have been guilty of this transgression. Wild reef life can often be collected through harmful means such as cyanide, and wild reef creatures often quickly die in captivity.
Therefore, reef aquariums will be useful teaching tools if only captive-bred fish and corals are used.
Beyond the realm of hobbyists, a reef aquarium could be a useful educational tool in schools. If used properly, a reef aquarium could teach students the importance of nature stewardship and the biology of natural ecosystems. A reef system also could help educate students in rudimentary physics and engineering if teachers demonstrated its plumbing. Setting up such a system may be expensive and time-consuming, but I believe it to be a worthy investment into enjoyable, hands-on learning that can be used for years. And the aquarium need not be a 400 gallon fish mansion. Even a 3 gallon reef aquarium would be a useful teaching tool.
- Based on coral reef footage found on Johnathan Bird’s Blue World:
- Bird, Jonathan.“Webisode 41: Coral Reefs.”Jonathan Bird’s Blue World. Jonathan Bird Productions & Oceanic Research Group, copyright 2009-2017. http://www.blueworldtv.com/webisodes/watch/coral-reefs. Accessed 24 Jun. 2017.
- “Corals.” National Oceanic and Atmospheric Administration, rev. 25 Mar. 2008. http://oceanservice.noaa.gov/education/kits/corals/coral02_zooxanthellae.html. Accessed 24 Jun. 2017.
- Adapted from the Coral Reefs page on WWF.com:
- “Coral reefs.” World Wide Fund For Nature. WWF, copyright 2017. http://wwf.panda.org/about_our_earth/blue_planet/coasts/coral_reefs/. Accessed 24 Jun. 2017.
- “Human Impact on the Reef: Importance of Coral Reefs.” Bio discovery and the Great Barrier Reef. Queensland Museum, 8 Jul. 2009. http://www.qm.qld.gov.au/microsites/biodiscovery/05human-impact/importance-of-coral-reefs.html. Accessed 24 Jun. 2017. i
- Status of and Threat to Coral Reefs. ICRI Forum. International Coral Reef Initiative. http://www.icriforum.org/about-coral-reefs/status-and-threat-coral-reefs. Accessed 24 Jun. 2017.
("Aquarium" photo, courtesy of Jake Mohan.)