Chapter 3: Perform aquarium techniques

Aquarium and vivarium techniques form an essential part of applied biology, particularly in Kenya where biodiversity conservation and research depend on controlled environments for aquatic and terrestrial organisms. Mastery of aquarium setup and maintenance supports ecological studies, breeding programs, and educational demonstrations. In professional settings such as university biology departments, county government research centers, and wildlife conservation projects, understanding the components and setup of aquaria ensures optimal conditions for organism health and experimental reliability. This chapter focuses on the practical aspects of aquarium components and the systematic process of setting up a functional aquarium.

3.1 Components of an aquarium

An aquarium is a closed, controlled habitat for aquatic organisms, and its parts do the work that rivers, lakes and the wider environment do for wild animals and plants. Water must be kept clean, moving, oxygen-rich and at a steady temperature, while the organisms in it need food, shelter and light. This topic describes the structure of the tank first, then the five main components of an aquarium in turn: the filter, the pump, the thermometer, the aquatic plants and animals, and the decoration. Putting the parts together and running the aquarium are covered in Setting up an aquarium.

Tank, cover and lighting

The tank is the container that holds the water, and its size decides how much equipment and how many organisms it can support.

• Tank material: Glass is hard, stays clear and resists scratching, but it is heavy. Acrylic is lighter and can be moulded into shapes, but it scratches more easily and needs soft cleaning pads.
• Volume: The water volume is found from the inside length, width and depth of the water. Example: a tank with water 100 cm long, 40 cm wide and 50 cm deep holds 100 × 40 × 50 = 200 000 cm³, and since 1 litre = 1000 cm³ this is 200 litres. The real volume is a little less because the substrate and decorations take up space.
• Weight and stand: Water weighs about 1 kg per litre, so the 200 litre tank carries about 200 kg of water alone. The stand must be level, strong and wide enough to carry the whole base.
• Cover or lid: A cover cuts evaporation, keeps out dust and insects and stops fish from jumping out, while leaving space for cables and air lines.
• Lighting: Lights supply the light that aquatic plants need for photosynthesis and set the day length for the animals. Fit them with a timer so the day length stays the same, and keep the tank out of direct sunlight, which overheats the water and feeds algae.

Heater and chiller

Temperature control depends on the climate of the room and on the species kept.

• A submersible heater with a thermostat keeps the water at the set temperature in rooms that become cool at night.
• In hot rooms, shading the tank, placing it away from sun and walls that heat up, and using fans over the water surface lowers the temperature, and a chiller is used where this is not enough.
• A heater is always matched to the tank volume, using the maker's chart, and it is never switched on out of the water.

3.1.1 Filter

A filter removes solid waste and dissolved wastes from the water, so the water stays clear and safe for the organisms. The animals produce ammonia, which is toxic, and the uneaten food and plant debris produce more. Filters treat the water in three ways, often in one unit.

Types of filtration

• Mechanical filtration: Foam, floss or sieve material traps suspended particles such as uneaten food and detritus, which would otherwise cloud the water and rot.
• Biological filtration: Beneficial bacteria live on the surface of porous media such as ceramic rings, sponge or sintered glass. They convert toxic ammonia first into nitrite and then into the much less harmful nitrate, a process called nitrification.
• Chemical filtration: Media such as activated carbon or resins take dissolved organic compounds, colours and some pollutants out of the water by adsorption.

Filter units

Installation and maintenance

• Choose a filter whose rated flow suits the tank. Example: a filter rated at 800 L/h on a 200 L tank turns the water over 800 ÷ 200 = 4 times an hour in theory, and less in practice as the media clog, so a margin is allowed.
• Arrange the media so that water meets the mechanical media first, then the biological media, and the chemical media last.
• Place the outlet so that the whole tank circulates, without a current that pushes small fish around.
• Rinse the mechanical media in water taken from the tank during a water change, never in tap water, which can contain chlorine that kills the bacteria on the media.
• Never clean or replace all the media at once, so that enough bacteria remain.
• Do not switch the filter off for long periods. When the flow stops for several hours, the bacteria can run out of oxygen and die, and the ammonia then rises.
• Replace chemical media according to the maker's advice, because exhausted carbon releases what it had taken up.

3.1.2 Pump

Pumps move water and air. Water pumps keep the water circulating through the filter and around the tank, and air pumps add air to improve oxygen levels. Without movement, water stratifies, waste settles in dead corners and the oxygen at the surface cannot reach the bottom.

Pump types and specifications

Use and troubleshooting

• Choose the pump from the tank volume, the height it must lift the water and the needs of the organisms. Delicate species need gentle flow.
• Place an air pump above the water level, or fit a check valve in the air line, so that water cannot siphon back into the pump when the power fails.
• Most of the oxygen enters the water at the surface, where bubbles stir the water, so surface movement matters more than a very fine stream of bubbles.
• A drop in flow usually means a blocked intake or a dirty impeller, and is cleared by switching off, unplugging and cleaning the parts.
• A rattling noise suggests air in the pump or a worn bearing and is checked early, before the pump fails.
• Run cables with a loop below the socket, so that water cannot run along the cable into the socket, and use a residual-current device. Unplug all equipment before putting hands in the water.

3.1.3 Thermometer

A thermometer shows whether the water is at the temperature the species need. Temperature controls the metabolism, feeding, growth and breeding of cold-blooded animals, and it also controls how much oxygen the water can hold, which falls as the water gets warmer. Many tropical freshwater fish do well at roughly 24 to 28 °C, but each species has its own range, so the target is taken from the species kept.

Types of thermometers

• Glass liquid-in-glass thermometers: Spirit-filled thermometers are accurate and cheap but break easily. Mercury thermometers are not used in aquaria, because a broken one releases a toxic metal into the water.
• Digital thermometers: A probe in the water sends the reading to a display, often with a high and low temperature memory and an alarm for deviations.
• Adhesive strip thermometers: A liquid-crystal strip on the outside of the glass gives a quick visual indication, but it reads the glass and is less accurate than the other types.
• Infrared thermometers: They read the surface temperature without touching, and in an aquarium they read the glass or the water surface rather than the water inside, so they are used only for quick checks.

Placement and calibration

• Place the thermometer at mid-depth, at the opposite end of the tank from the heater and away from the filter outlet, where the water is mixed but not at the extreme temperature.
• Read it at the same time every day and write the reading in the tank log.
• Check the thermometer against a reference thermometer, or in a mixture of crushed ice and distilled water, which should read 0 °C. A thermometer that reads wrongly is replaced or its error is noted.
• A steady temperature slightly off the ideal is less harmful than large swings, so a rapid change in the reading is investigated at once.

3.1.4 Aquatic plants and animals

The living things in an aquarium are the reason for the rest of the equipment. Plants and animals are chosen together so that they share the same water conditions and can live in the space provided. Plants produce oxygen in the light, take up ammonia and nitrate, give cover and compete with algae for nutrients. At night plants use oxygen, so heavy planting in a tank without enough aeration can lower the oxygen before morning. How organisms are put into the tank is dealt with in Introducing aquarium organisms.

Criteria for selection

• Species compatibility: Animals that eat each other, harass each other or compete for space cannot be kept together. Size at adult age, not size when bought, decides compatibility.
• Environmental requirements: Temperature, pH, hardness, light and flow tolerances of every species must overlap with the conditions of the tank.
• Space and stocking: The tank must hold the adult size of the animals, and the oxygen supply and the filter must cope with their waste. Overstocking quickly degrades water quality, so stocking is planned from adult size and not added up from what fits at purchase.
• Purpose: For research, the species is the one under study. For display or teaching, the species are chosen to show the features and behaviours to be taught. A species chosen for a study of territorial behaviour, for example, may grow large and need a tank much bigger than its size at purchase suggests.
• Legal and ecological considerations: Collect from the wild only with the permits that the law requires, and obtain stock from licensed breeders when possible. Never keep invasive species such as water hyacinth (Eichhornia crassipes) or salvinia (Salvinia molesta), which have spread widely in Kenyan waters, and never release aquarium organisms into natural waters.
• Maintenance needs: Choose species whose feeding, water and temperature needs can be met for their whole life with the resources of the facility.

Aquatic plants

• Rooted plants: Vallisneria and similar plants root in the substrate and need nutrients there.
• Plants attached to wood or rock: Java fern and Anubias grow on a rhizome that must stay above the substrate, and they tolerate low light.
• Floating and stem plants: They take nutrients straight from the water and compete well with algae, but floating plants shade the water and must be thinned.
• Plant care: Remove dead leaves, trim overgrown stems, and check that the lighting and the available nutrients match the plants chosen.

3.1.5 Decoration

Decoration gives the aquarium physical structure. It provides hiding places, territories, spawning sites and surfaces for beneficial bacteria and algae, and it lets the animals show natural behaviour. Animals in a bare tank are more likely to be stressed and timid.

Types of decoration

• Substrate materials: Sand or gravel covers the bottom, anchors the plants and carries bacteria. Fine sand suits animals that dig, and rounder gravel is easier to keep clean.
• Rocks and stones: Smooth, inert rocks give shelter and mark out territories. Rocks that contain limestone dissolve slowly and raise the hardness and pH of the water, so they are not used in tanks for species that need soft, acidic water. A few drops of vinegar on a rock that fizzes show that it contains carbonate.
• Wood: Cleaned driftwood or bogwood gives shelter and a surface for biofilm, but it may release brown tannins that stain the water and lower the pH slightly.
• Artificial plants and ornaments: They provide cover where real plants cannot grow, but they must be non-toxic, with smooth edges.
• Background: A coloured or natural background on the back of the tank reduces stress and hides cables and equipment.
• Functional decorations: Breeding caves, pots or lengths of pipe give spawning and nesting places for species that need them.

Selection and maintenance

• Use only materials made for aquarium use or known to be inert and non-toxic, and never paint, varnish or treated wood.
• Rinse new substrate, rocks and ornaments in clean water until the water runs clear, and never use soap or detergent on them.
• Arrange the structures so that they cannot topple and trap or crush animals, and leave open water for swimming.
• Inspect decorations regularly for rotting, algae, sharp edges or loose parts, and clean them in water taken from the tank, not in tap water.

Chapter Summary

This chapter explores the essential components that make up an aquarium, starting with the filter which maintains water cleanliness by removing impurities. The pump is discussed as a vital element for circulating water and ensuring adequate oxygenation for aquatic life. Accurate temperature monitoring is achieved through the thermometer, which helps maintain a stable environment for aquatic plants and animals. The chapter highlights the importance of selecting suitable aquatic plants and animals that coexist harmoniously within the aquarium ecosystem. Decoration is also covered as a means to create a visually appealing and natural habitat. The final section provides detailed guidance on setting up an aquarium, emphasizing the correct assembly and arrangement of these components to support a healthy and balanced aquatic environment.