Aquarium Niche

Saltwater aquarium: Hosts a variety of colorful aquatic species (1)

An aquarium 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]. 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].

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.

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].

The brackish water can be found in an estuary, a body of water where freshwater from the stream meets the open sea [2]. The salinity of the water varies from 1 ppt to 36 ppt due to the interactions between freshwater and saltwater. For example, salinity of the estuary can be affected by freshwater from the rain or the river [2]. Bacteria used in filtration, such as Nitrosomonas and Nitrobacter, cannot tolerate these changes; hence, in the aquarium, it is normal to have a stable salinity level [3].

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, Scats, Archerfisher, Pufferfish, 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, Lilaeopsis brasiliensis, Bacopa monnieri, and Cryptocoryne ciliata [3]. However, some freshwater plants can adapt to the salinity of the brackish water, including Vallisneria gigantea, Anubias barteri, Hygrophila polysperma, Ceratophyllum demersum, Crinum thaianum, and Cryptocoryne wendtii [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].

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.

Nitrobacter is

Nitrosome is

The Microbes 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.

MICROBES OF THE NITROGEN CYCLE

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 mentioned above 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.

pH

The ideal pH for these beneficial bacteria is between 7.2 and 8.5, having a narrower range than tolerated by fish.

Temperature

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.

Oxygen

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.

Light

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.

Salinity 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.

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.

Are there any other non-microbes present?

Plants? Animals? Fungi? etc.

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.

'Super' bacteria live on sheets, fingernails: study

On June 6, 2005, U.S reserachers

References

1. "aquarium_600.jpg". NOAA: Ocean Explorer. 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