Aquarium Niche

Introduction to Aquarium

Saltwater aquarium: Hosts a variety of unique aquatic species. Picture taken from National Oceanic and Atmospheric Administration (NOAA). (1)

An aquarium (plural form is aquaria or aquariums) is an artificial ecosystem that is inhabitable by various aquatic species. The environment of the aquarium can differ depending on the residing species. For example, Xiphophorus helleri or Green Swordtail prefer to live in freshwater, while Paracanthurus hepatus or Surgeonfish prefer water with higher salt concentration [2]. Nothing quite adds to the room décor as adding an aquarium with beautifully colored fishes with lively aquatic plants. However, what keeps these colorful organisms alive and healthy are none other than the series of micro-organisms, also known as microbes. However, aquariums are built as an “ideal” ecosystem; thus, filtering out most of the microbes that can be found in natural body of water. For example, ultraviolet sterilization are used in aquariums to destroy algae and nucleic material of many free-floating micropathogens [8]. Furthemore, most of the work done by natural microbes is conducted by machines or by adding chemicals. Thus, taking away reasons for having microbes, that can potentially become harmful to the inhabitants, in the aquarium.

What kind of microbes can survive such controlled environment? Do aquariums need microbes? What happens if bacteria are introduced into the aquariums? The focus of the topic is to discuss the microbes that can survive in the aquarium, and how they affect the ecosystem. In addition, the topic covers the different type of aquariums and its condition, and the non-microbes that inhabit the aquaria ecosystem.

Maintaing Aquaria Niche

Aquarist must maintain specific pH, temperature levels, and lighting for different species in the aquarium. Salinity, the concentration of salt in a given amount of water, becomes one of the characteristics to distinguish between the different types of aquariums. Salinity can be measured using a hydrometer, which compares the specific gravity of sample with pure water under the units of ppt (parts per thousand) or ppm (parts per million) [2]. In addition, the aquarium's hardness must be monitored. The levels of dissolved minerals, such as bicarbonates, in water is described as the water's hardness [2].

Types of Aquarium Niche

Commercial aquariums come in variety of shapes and sizes, from tiny one gallon fish bowls to luxurious 100 gallon fish tanks, and normally can be set simply on a desk top or on top of a special aquarium stand. There are generally four types of aquariums a new aquarist can set up: tropical freshwater, cold freshwater, brackish, and saltwater. Each type of aquarium requires specific care and maintenance, and different types of fish reside in each of the designed ecosystem.

Tropical Freshwater Aquarium

In tropical freshwater aquariums for fish such as tetras and gouramis, the temperature must be kept at 72 - 80 °F (22 -27 °C). The pH must be kept between 6 and 8, the stability and the consistency of the pH also playing an important role in ensuring the health of the fish. Since freshwater fish normally cannot tolerate any salinity, salinity must be kept under 3ppm (parts per million).

Cold Freshwater Aquarium

In cold freshwater aquariums for fish such as goldfish and koi, the temperature should be kept typically below 70 °F (20 °C). The light should be kept at the standard level and the hardness of the water at 100-200mg/L CaCO3.

Brackish Water Aquarium

Brackish-water Aquarium [4]

Brackish water aquarium is an artificial ecosystem that simulates the natural environment of brackish water, which has a salt concentration between freshwater and saltwater. Brackish water aquarium is kept at a temperature around 23-29°C, with a pH between 7 to 8, a hardness of 200 mg/liter of CaCO3, a specific gravity of 1.003-1.012, and a salinity between 7.6 and 14 ppt [2].

Brackwish water can be found in Central American costal streams, East Africa mangrove swamps, and Southeast Asia estuaries [2]. A large variety of species inhabit the brackish water, such as Sailfin, Monos, and Cichlids [3]. Planting in Brackish water aquarium is difficult because there are limited number of brackish water tolerant plants being distributed. This includes Microsorium pteropus, Crinum calamistratum, Bacopa monnieri, and Cryptocoryne ciliata [3].

Influence by Adjacent Communities (if any)

Is your niche close to another niche or influenced by another community of organisms?

Conditions under which the environment changes

Do any of the physical conditions change? Are there chemicals, other organisms, nutrients, etc. that might change the community of your niche.

Microbes that Inhabit the Aquarium

Public aquariums can host large varieties of aquatic species in a closed and “ideal” ecosystem. However, there are numbers of microorganisms in nature that are not present in aquariums despite their profound importance to global marine ecology [5]. This is mainly due to the difficulty in creating a habitat for the microorganisms, and, at the same time, maintaining a suitable environment for the aquatic species [5]. In the aquarium, bacteria are mostly responsible for breakdown waste [6]. The most frequent process is the breakdown of protein into ammonia, then nitrite into nitrate [6]. This process of waste disposable is known as the Nitrogen Cycle.

Microbes Involved In Nitrogen Cycle

The waste excreted by the fish in the aquarium must always somehow be kept low at a non-toxic level. The cycle that exists in aquariums and natural aquatic environments alike is the nitrogen cycle. Since an aquarium is a fragile ecosystem on average containing only 10 gallons of water, it requires the aquarist’s interference in ensuring that the cycle is well established. In so doing, one must create this artificial ecosystem as close to the natural environment as possible. Only when all the players of the nitrogen cycle have successfully been established can more fish be added with a minimal loss.

Nitrosome and Nitrobacter
Nitrosomonas europea is a Gram-negative chemolithoautotroph that can derive all its energy needed for growth by the oxidation of ammonia. They colonize in other environments such as soil, sewage, and walls of buildings. Nitrobacter is also a Gram-negative chemoautotroph. Both of the nitrifying bacteria require specific environment for their maximum activity, all of which should be met by the environments the aquarist sets up for the fish in the aquarium. Because these organisms cannot form spores, the aquarium must be kept at the optimum condition at all times for the biological filtration of these nitrifying bacteria to function. They also form slimy biofilms in order to protect themselves from dessication and other potential threats.

The ideal pH for these beneficial bacteria is between 7.2 and 8.5, having a narrower range than tolerated by fish. They are most active between the temperature of 68 - 86 °F; 50°F is the minimum temperature and 95°F is the maximum temperature for these nitrifying bacteria. Nitrifying bacteria are aerobic organisms and oxygen is critical for their nitrifying activity. As the oxygen level decreases beyond 1mg/L, dissolved oxygen becomes the limiting factor of the nitrification reactions. Thus, the oxygen level in the water must be at least 2mg/L in order for it to not have an adverse effect on the nitrifying activity.

Nitrifying bacteria are light sensitive, especially to UV light contained in the sun light. Room light can also have an adverse effect on the bacteria. Light is thought to oxidize cytochrome C, an electron carrier. Thus, nitrifying bacteria tend to form colonies within the filteration system and beneath the gravel to avoid exposure to light. Nitrifying bacteria can tolerate a wide range of salinity. Thus, a beneficial bacterial colonies established in a freshwater environment can then be used for aquariums in a saltwater environment. This transition, though, must be carried out in a gradual manner for it to be effective. Maximum change of 5ppm should not affect the activity of the nitrifying bacteria. Thus Nitrosomonas and Nitrobacter are both seen in all of the four general types of aquariums mentioned in the previous section.

The Nitrosome and Nitrobacter in the Environment

The first step in the nitrogen cycle is the excretion of waste by the fish. There are two types of the waste excreted by the fish: carbon dioxide and nitrogenous compounds. Carbon dioxide that is returned to the water via fish’s gills is then used as a primary carbon source by the photoautotrophs present in the tank. These organisms include algae and aquatic plants. Nitrogenous compounds that are excreted by the fish are usually in the form of ammonia, which is very toxic to the fish. This ammonia is then turned into ammonium ion in water via the following equation:

NH3 + H2O ↔ NH4+ + OH-

This equation is driven to the right if the ammonium ion present is constantly being diminished by another organism.

The second step in the nitrogen cycle is the conversion of the ammonium ions into nitrites. This step is carried out by a class of bacteria called nitrifying bacteria via a process called nitrification by the following oxidation reaction. The genus of bacteria involved in this step of the cycle is Nitrosomonas, specifically Nitrosomonas europae.

NH4+ + 3/2 O2 ↔ 2H+ + H2O + NO2-

In the third step, the nitrites are then converted into nitrates by another example of nitrifying bacteria, specifically of the genus Nitrobacter by the following oxidation reaction:

NO2- + 1/2O2 ↔ NO3-

Nitrates, then, are in part used as fertilizers by aquatic plants and algae. The rest can sufficiently be removed by the water changes carried out by the aquarist since nitrates are relatively non-toxic to the fish.

Which microbes are present?

You may refer to organisms by genus or by genus and species, depending upon how detailed the your information might be. If there is already a microbewiki page describing that organism, make a link to it.

Do the microbes that are present interact with each other?

Describe any negative (competition) or positive (symbiosis) behavior

Do the microbes change their environment?

Do they alter pH, attach to surfaces, secrete anything, etc. etc.

Do the microbes carry out any metabolism that affects their environment?

Do they ferment sugars to produce acid, break down large molecules, fix nitrogen, etc. etc.

Non-microbes in Aquarium

Aquarium Plants

Aquarium plants are important for the ecosystem of the aquarium, since most aquatic species live side by side with vegetations. Plants can provide shelter, food, breeding sites, nest-building materials, and territory markers [2].

Photosynthesis is one of the most important functions of aquarium plants: 6 CO2 + H2O + Light (Energy) --> Glucose + 6 O2. Simply put, aquarium plants consume carbon dioxide, and, with the presence of light, produce oxygen. The amount of light used in the aquarium can affect the plant’s photosynthesis. With sufficient illumination, the consumption of carbon dioxide and production of oxygen are high in aquarium plants [8]. The result is a drop in carbon dioxide level in water and rise in oxygen concentration [8]. When the aquarium lights are turned off (night time), respiration slows down. As a result, there is a drop in dissolved oxygen concentration, and increase in carbon dioxide in the water [8].

Plants are also important in maintaining the health of fishes. Plants remove not just certain mineral salts from the water, but also significant quantities of organic carbon compounds and even phenols [8]. They can reduce the number of certain bacteria that lead to health issues [8]. Some plants, such as Lemna spp. or duckweed, can produce antibiotics, while others can keep some damaging molecules, such as nitrates and phosphates, under control [8].

Algae

Green algae are seen in all the aquarium environments. Picture taken by David Burdick. NOAA distributed. (9)

Algae are non-flowering, photosynthesizing plants that grow in most body of water. Algae are seen as problematic in aquariums because they compete with aquaria plants for nutrients and space, and create unfavorable environment for the inhabitants, such as increasing the nitrate levels [8]. However, algae provide food to a number of aquatic species, and can be used to test the growing conditions of the aquarium (allows aquarist to decide whether the aquarium is ready to inhabit plants and fishes). There are various types of algae that can grow in aquariums: blue-green, green, red, and brown algae.

Patches of red and green algae on rock surface. Picture taken from NOAA Ocean Explorer. (7)

Blue-green algae are cyanobacteria that have the characteristics of both bacteria and algae. They can form rapidly and cover plants, leading to plant death [8]. Blue-green algae are seen in new aquariums that contain “raw” water, thinly planted, excessively illuminated with lights, and contain water pollutants [8]. Green algae can be free-floating single-celled or attached filamentous/encrusting types [8]. They can be found in aquariums with high illumination. Free-floating will cause green-water problems, while filamentous type produce tuft-like growths on plants [8]. However, they can act as food source for some fish species, such as Gyrinocheilus aymonieri or Sucking Loach [8]. Despite the name, red algae (also known as fir or brush algae) are greenish-brown, and forms tufts on plants and decorations [8]. Red algae form under aquarium with lower illumination because they are naturally found in deeper water with less light [9]. Brown algae form brown encrustations on aquarium panes, decorations, and plant leaves [8]. They are mostly seen in aquaria with poor plant growth [8]. Similar to red algae, brown algae grow in low illumination.

References

1. NOAA Ocean Explorer. "aquarium_600.jpg". 2006. Washington D.C., 26 August 2008. <http://oceanexplorer.noaa.gov/explorations/04fire/logs/april05/media/aquarium.html>.
2. Scott, Peter W. The Complete Aquarium. New York: Alfred A. Knopf Inc., 1991.
3. Monks, Neale. Brackish FAQ. 2007. 20 August 2008. <http://homepage.mac.com/nmonks/Projects/brackishfaq.html>.
4. "p25%20Mangrove%20community.jpg". A Tour of China in Winter: Part 4b, A Visit to the Shanghai Ocean. Aquarticles. 25 August 2008. <http://www.aquarticles.com/articles/travel/Norfolk_4bChina_Shanghai_Aquarium.html>.
5. Consi, T.R. Marine Technology Society. Marine Technology Society Journal [0025-3324] yr:2001 vol:35 iss:1 pg:36 -47
6. Wiegert, J. Freshwater and marine aquarium [0160-4317]. yr:2006 vol:29 iss:3 pg:112 -116
7. NOAA Ocean Explorer. "bacteria_algae_600.jpg". 2006. Washington D.C., 28 August 2008. <http://oceanexplorer.noaa.gov/explorations/04fire/logs/april08/media/bacteria_algae.html>
8. Dawes, John. Complete Encyclopedia of the Freshwater Aquarium. Ontario, Canada: Firefly Books Ltd., 2001.
9. Burdick, David. NOAA's Coral Reef Data. "algae_186.jpg". 2006. Washington D.C., 28 August 2008.