Aquarium Furnishings

Gravel: The gravel in the serves both an aesthetic and a practical purpose. The gravel in the tank provides support for plants, a means of filtration with undergravel filter systems, and a region for fish to carry out activities such as breeding and feeding.

The composition of the gravel is important in that gravel that contains minerals will dissolve and harden the water. In some cases with African Rift Lake fish, water-hardening substrates are acceptable, but for many fish and plant species, the increasing water hardness is detrimental. Suitable substrate materials for the aquarium include river sand, quartz gravel, basalt, and gravels that are available in aquarium shops.

If plants are kept in the tank, the gravel should be 2-5 mm in diameter. Many aquariasts, who raise plants, layer the gravel. On the bottom is placed 5-10 mm size gravel, followed by base fertilizer (available at aquarium stores) like laterite, followed by a layer of 5-7 mm size, and finally a top layer of 2-4 mm size gravel. The result is a 3" (8 cm) gravel depth with a composition that in which plants can thrive.

The gravel can be added to the tank and arranged levelly or terraced. To terrace the gravel, use flat rocks, wood, or glass strips. Before adding the gravel to the tank, the gravel should be carefully washed to remove all small particles.

Rocks: The tank should be furnished with rock structures to provide hiding and breeding places for fish. The rocks used should not dissolve or crumble in water, nor release calcium. When constructing rock structures, be sure that they are stable and will not collapse on burrowing fish. Perhaps the best way to construct rock structures is to place the rocks on a thin layer of Styrofoam (directly on the tank floor), secure them, and then cover the Styrofoam and base of the rocks with gravel. Suitable types of rocks for the aquarium include lava, sandstone, slate, granite, basalt, and quartz.

Wood: Wood provides a refuge, a spawning site, and nourishment for some catfish. Wood can further add to the acidity of the water, benefiting fish that prefer acidic water. Only use bog wood for the aquarium, as most other wood will rot in aquaria. Do not use wood in tank with fish that require hard, alkaline water, as the wood will affect the alkalinity.

Plants: Please see the section on plants for details.


Lighting: The type of lighting is not especially important if plants are not grown. Almost any incandescent or fluorescent light does fine. Do not only use colored incandescent lights for tropical fish as these cause ill effects. To minimize algal growth, only light the tank for 10-12 hours a day.

Plants require light in order to carry out photosynthesis and grow. Plants require more light, for a longer period of time (12-14 hours) than a tank housing only fish. The light hood should have a reflector, and the light equipment should be UL approved. The strength of lighting should be about 1 watt per gallon of water. There are several types of bulbs that can be used, although fluorescent and mercury vapor lamps are the most practical.

    (1) Fluorescent tubes -- Fluorescent tubes are the most popular type of bulb among aquariasts with plants. Fluorescent tubes consume little power, produce little heat, and provide an even distribution of light. Fluorescent tubes are available in a wide range of types including full-spectrum bulbs. Light output can be increased by using a reflector or foil on the ceiling of the hood to reflect more light to the tank. One draw back to fluorescent lights is that their intensity decreases with time. Sometimes this decrease is not noticeable to the keeper, but still affects plants. Thus fluorescent tubes should be replaced every six months. Fluorescent lights are not usually strong enough to light a tank taller (deeper) than 20" (50 cm).

    (2) Mercury vapor lamps -- Mercury vapor lamps are not that common, although they work well for tanks with a depth greater than 20" (50 cm). These lights require special fixtures. In tanks deeper than 20" (50 cm) use about 6.25 watts per inch.
To control the amount of lighting each day, a timer can be purchased. Set the timer so that the light is on for 12-14 hours. Another beneficial device is a dimmer switch which can be used to vary the levels of light.

Heater: The most popular means to heat the aquarium is a glass immersion heater. There are two types of glass immersion heaters, non-submersible and submersible. The submersible heaters are a better investment, because they are usually more reliable and need not be unplugged whenever the water drops more than 6" (15 cm) from the top. With both types, the heater must be unplugged for 10 minutes before it leaves the water. If the heater is immersed it is subject to breakage. These types of heaters are generally fairly inexpensive. Be sure to use the right size heater for the tank: 2-3 watts per gallon of water is usually suggested. If possible, place the heater in the filter unit (wet-dry filter), so that the clean, incoming water is heated. The fish cannot be burned when the heater is in the filter.

Most heaters include a thermostat, so that once the temperature is set, the temperature does not vary much. In order to set the temperature with one of these units, place the heater into the water and let it sit for 10-15 minutes. Then plug in the heater and let it run until the tank reaches a constant temperature and the pilot light (indicates the heater is running) turns off. Then read the temperature on the thermometer and adjust the heater accordingly.

When working in the tank, always unplug the heater for safety reasons. Some fish species may rest or hide on the heater. These fish often receive burns. To prevent this problem, protect the fish by surrounding the heater with a mesh, cage-like structure. Some authors have suggested wrapping the heater with plastic airline tubing.

Two other heating devices are available: undergravel (cable) heaters and heaters that use electronic thermostats. Undergravel (cable) heating systems are most popular for the aquariast having plants, as this heating system creates circulation through the gravel. These are generally expensive, although they are safe and will not burn fish. Heaters using electronic thermostats are a new innovation. These highly accurate, but expensive heaters are excellent.

Thermometer: Always use a reliable thermometer to monitor the aquarium's temperature. Several types are available including stick-on liquid crystal types, floating glass types, and electronic (digital) types. The liquid crystal type is convenient in that it is easily read when affixed to the side of the tank, but is not entirely accurate because it can be influenced by temperatures outside of the tank. Glass type thermometers can either float or sink, depending on the type. Again, these are not that accurate but will serve the need of most aquariasts. The most accurate, easiest to use, but most expensive of the three types is the electronic (digital) thermometer. This type of thermometer gives you a reading every few seconds, and is usually accurate to � 0.1�F.

Air Pump: The air pump is an important part of the aquarium, especially if there is no power filter to create surface disturbance for oxygenation. The air pump can be used to power air stones which drive undergravel filters, internal box filters, and sponge filters. Separate air stone can be used for further aeration. The major drawback to air pumps is the noise they produce, especially when they are vibrating against something. Less expensive models are often noisier than higher quality, more expensive models.

Filtration: The filter is one of the most important pieces of equipment in the aquarium. The filter is the device that must be capable of handling fish waste and particles in the aquarium. The filter should have three means of filtration: mechanical, chemical, and biological.
    - Mechanical filtration refers to the filtering of water through a strainer or filter media, such as filter wool or foam, to remove particles from the water. After four weeks, the mechanical filter media begins to serve as biological filtration as bacteria cultures colonize the media. Activated carbon serves as a means of mechanical filtration by absorbing small particles including toxins, medications, and some fish wastes.

    - Chemical filtration refers to the process of removing particles or altering water conditions by chemical means. One popular material for chemical filtration is ammonia absorber (zeolite) which binds to free ammonia. Ion exchange resins reduce the water hardness by removing salts from the water, thus lowering the pH and softening the water. Peat is used in a similar way to bring down the pH and reduce hardness for species that prefer "blackwater" conditions. Nitrate absorbers are a new product that binds nitrates to render them less toxic. Many chemical filter medias only work for a period of time before they are saturated. Most of these can be "recharged" in a soaking in a salt water solution.

    - Biological filtration is the most important function of the filter. Nitrifying bacteria (see Water Chemistry) break down organic wastes from ammonia to nitrite to nitrate. Without biological filtration, ammonia is present from the fish excrement, excess food, and plant matter. This is why newly established tanks must "cycle" (build up a culture of nitrifying bacteria) before expensive fish are introduced. Bacteria need plenty of oxygen to do their work, and most quality filters provide an adequate supply. The larger the surface area of the media, the more area for bacteria to interact with organic compounds. Thus most media for biological filtration are porous or in irregular shapes to provide more surface area. Biological filter media should be rinsed only every month or two with cool to luke warm water, so as not to kill off too much of the beneficial bacteria. If there are two biological filter containers, clean only one at a time, so less there is disruption of biological filtration.
The filter should also provide oxygen for the fish. With a good filter, no air stone should be necessary. Most motorized filters achieve aeration by surface disturbance. The amount of oxygen dissolved in the aquarium can be proportional to the amount of surface disturbance (the more disturbance, the more gas exchange). Some fish species, those inhabiting streams, creeks, and flowing rivers, prefer water with current. Water current can be created by the filter, especially power heads, internal power filters, circulating pumps, and spray bars from canister filters.

The filter should be large enough to handle the amounts of wastes produced by the fish and plants in the tank. Many filters are rated in terms of "gallons (liters) per hour." Use a filter that is rated to pump five to six times the tank's capacity an hour. For example, a 20 gallon tank should be equipped with a filter that pumps at least 100-120 gallons an hour.

Types of Filters: There are numerous types of filters available today.
    - Undergravel filter: The undergravel filter is the most common filter in the United States. Most tank purchased "complete" include an undergravel filter system. Undergravel filters are simple to operate. They consist of plates that are covered with gravel and one or more up-right tubes. The filter is powered by an air pump via an air stone in the up-right tube. As the air bubbles move up the tube, water is also drawn up the tube. This action creates a vacuum-like movement that causes tank water to pass through the gravel bed, under the plate, and up the tube. As the water moves into the gravel bed, wastes are trapped in the gravel and broken down by nitrifying bacteria. Undergravel filters often incorporate chemical filtration through the use of a detachable cartridge near or at the top of the up-right tube.

    - Powerhead: The powerhead operates with an undergravel filter system. The powerhead is a motorized filter that is placed at the top of the up-right tube. Powerheads pump water from the up-right tube into the tank creating a suction that pulls water though the gravel bed and up the tube. Powerheads are able to move water much faster than the conventional air-driven stone, and can create strong water currents.

    Alternately, some place a sponge on the base of the powerhead, causing the powerhead to act as a "turbo" sponge filter. The powerhead pumps water out into the tank and intakes water through the sponge. Debris is trapped in the sponge. This system is not suitable for larger aquariums with medium to large fish loads. Most powerheads also aerate sufficiently so that an air pump is not necessary.

    - Sponge filter: A sponge filter is also powered by air. A sponge filter consists of a tube, a sponge, and a place for air-line connection. Air is pumped into the tube, creating a vacuum, and causing water to pass into the tube through the sponge. In the process, debris in the water is trapped in the sponge where the debris is broken down by bacteria. Sponge filters are only suitable for small tanks having a small fish load, because they do not have the capacity to handle much waste.

    - Reverse Flow Powerhead: Reverse flow powerheads can be used in conjunction with an undergravel filter system. A sponge is placed on the powerhead, and the out flow of the powerhead is funneled into the up-right tube of an undergravel filter. Thus the powerhead pumps water down the up-right and under the undergravel plate and up through the gravel. Debris in the tank is sucked into the sponge where it can be broken down by bacteria.

    - Internal corner box filter: An internal box filter is powered by an air pump. The air bubbles create a current that draws water and debris into the filter, which usually contains foam or cotton. This type of filter is only suitable for small tanks with small fish loads.

    - Internal (submersible) power filter: An internal (submersible) power filter operates on the same principle as an internal box filter, but utilizes a motor. These filters are more suitable to larger tanks and larger fish loads than air-powered internal filters.

    - External power (back) filter: An external power or back filter is a popular filtration system. This filter consists of an intake tube, a hanging box, filter media, and a passage for water out-flow. This type of filter fits on the back of the fish tank, so some clearance between the tank and wall is required. The operation of the filter is simple: the motor creates a siphoning action which causes water to enter the filter. The water passes through the filter media (ranging from carbon to to materials increasing surface area for bacteria growth) and out the water return. The returning, oxygenated water creates a moderate current. When the tank level is a few inches low, the returning water cascades, creating a "waterfall-like" sound. Back filters are generally cost efficient.

    - Canister filter: The canister filter is an increasingly popular filter. The canister filter consist of a canister, which can be placed in a cabinet below the tank, and intake and output hoses. Water is taken in by the filter (via the intake hose), filtered through media in the canister, and returned through the out-put hose to the tank. The returning water can enter as a stream, a rain-like dripping, a slow current, or a spray, depending on the end-piece. Canister filters are excellent filtration systems as they have a great deal more surface area than back filters, and they are quiet and inconspicuous. Canister filters should be maintained on a regular basis, or as directed by the manufacturer's instructions. Usually canister filters do not need to be cleaned as regularly as other filtration systems, because canister filters rely most on biological filtration. Do not clean all the filter media at once because too much of the beneficial bacteria will be disturbed.

    - Diatom filter: Diatom filters are less used than canister or wet-dry systems; they are mostly used for infrequent cleaning of dirty tanks. Using diatomaceous earth, these filters are able to trap tiny particles. Because diatom filters are usually only used for spot cleanings, there is not time for bacteria to build up. Thus, diatom filters most often serve for mechanical filtration.

    - Wet/dry filter: Wet-dry filters are the best biological filters available. Numerous commercially produced types are available, although many hobbyists produce their own. Although there are numerous different designs, wet-dry filters are all based on the same principle: biological filtration by providing immense area for gas exchange. Usually wet-dry filters consist of filter media (arranged in trays, or by other means) though which, water drips. The media is kept constantly moist, but exposed to oxygen at the same time. Many systems have a pool of water where the heater can be kept, so water returning to the aquarium is heated.
Bucket: A bucket is needed for water changes and adding water. A 2.5 to 3 gallon (about 10-12 L) bucket is sufficient. The bucket should be used only for the aquarium.

Siphon Hose: A siphon hose is needed for water changes. Siphon hoses are available in a range of sizes and designs: from inexpensive hoses to long hoses used for both emptying and filling.

Net: Every fish owner should have at least one (preferably more). The net should be fine mesh designed for aquarium use.

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