THE AQUARIUM

Aquarium Furnishings

Gravel: The gravel in the tank serves both an aesthetic and a practical purpose. It provides support for plants, acts as a filtration medium in undergravel filter systems, and creates a habitat for fish to engage in activities such as breeding and feeding.

The composition of the gravel is important, as some types contain minerals that dissolve and harden the water. In certain cases, such as for African Rift Lake fish, water-hardening substrates are acceptable. However, for many other fish and plant species, increasing water hardness can be detrimental. Suitable aquarium substrate materials include river sand, quartz gravel, basalt, and commercially available aquarium gravels.

For planted tanks, the gravel should be 2-5 mm in diameter. Many aquarists who cultivate plants use a layered substrate approach. The base layer consists of 5-10 mm gravel, followed by a layer of base fertilizer (such as laterite, available at aquarium stores), then a layer of 5-7 mm gravel, and finally a top layer of 2-4 mm gravel. This creates a total substrate depth of approximately 3 inches (8 cm), which is ideal for plant growth.

The gravel can be arranged levelly or terraced using flat rocks, wood, or glass strips. Before adding gravel to the tank, it should be thoroughly washed to remove fine particles.

Rocks: Rock structures in an aquarium provide hiding and breeding areas for fish. The selected rocks should not dissolve, crumble, or release calcium into the water, as this can alter water chemistry. When constructing rock formations, ensure stability to prevent collapses, especially if the tank houses burrowing fish. A good method for stabilizing rock structures is to place them on a thin layer of Styrofoam (directly on the tank floor), secure them, and then cover the Styrofoam and rock bases with gravel. Suitable aquarium rocks include lava rock, sandstone, slate, granite, basalt, and quartz.

Wood: Wood serves as a refuge, a spawning site, and a food source for some catfish. Additionally, it can lower the pH and increase water acidity, benefiting fish that prefer soft, acidic water. Only use bog wood in aquariums, as most other types of wood will decay over time. Avoid using wood in tanks with fish that require hard, alkaline water, as it may alter water chemistry.

Plants: Please see the section on plants for details.



Accessories

Lighting: The type of lighting is not particularly important in tanks without live plants. Almost any incandescent or fluorescent light will suffice. However, avoid using only colored incandescent lights for tropical fish, as they can have adverse effects. To minimize algal growth, limit tank illumination to 10-12 hours per day.

In the early 1990s, aquarium lighting options were primarily limited to incandescent and fluorescent lights. Since then, technological advancements have introduced more efficient and versatile lighting solutions, most notably Light Emitting Diodes (LEDs).

Lighting Considerations: For aquariums without live plants, the type of lighting is not especially critical. However, avoid using colored incandescent lights for tropical fish, as they can have negative effects. To minimize algal growth, limit lighting to 10-12 hours per day.

For planted aquariums, proper lighting is essential for photosynthesis and plant growth. Plants generally require more intense lighting for extended periods—typically 12-14 hours per day. A light hood equipped with a reflector is recommended, and all lighting equipment should be UL-approved. While traditional guidance recommended approximately 1 watt per gallon of water, modern lighting technologies emphasize light intensity and spectrum rather than wattage.

Modern Lighting Options:

• Fluorescent Tubes: These remain popular among planted tank enthusiasts due to their energy efficiency, minimal heat production, and even light distribution. They are available in various types, including full-spectrum bulbs. Light output can be enhanced with a reflector or foil inside the hood to direct more light into the tank. However, fluorescent lights may not be effective in tanks deeper than 20 inches (50 cm). Their intensity decreases over time, so replacing tubes every six months is recommended.
• High-Output Fluorescent Lights: Modern fluorescent options such as Very High Output (VHO), Power Compact (PC), and T-5 High Output (HO) fluorescents provide higher light intensity, making them suitable for deeper tanks or setups requiring more illumination. They retain the benefits of standard fluorescents, such as energy efficiency and low heat production, while offering improved performance.
• Metal Halide Lamps: These lamps are effective for tanks deeper than 20 inches (50 cm) due to their intense light penetration. However, they require special fixtures, generate significant heat, and consume more energy. A general guideline for deep tanks is to use about 6.25 watts per inch.
• LED Lighting: LEDs have become the preferred choice for aquarists due to their energy efficiency, long lifespan, and versatility. They produce minimal heat and offer customizable light spectrums, which can be tailored to specific plant and fish requirements. LEDs can also simulate natural lighting conditions, such as sunrise and sunset, enhancing the aquarium’s aesthetic and supporting the well-being of its inhabitants. Although LEDs may have a higher initial cost, their long-term energy savings and durability often offset the investment.

• Glass and Quartz Submersible Heaters: Traditional and widely available, these heaters feature built-in thermostats for temperature regulation. Modern quartz versions are more durable and resistant to breakage.
• Titanium Heaters: More durable than glass heaters, titanium heaters are shatterproof and often include external controllers for easier adjustments.
• Inline Heaters: These heaters integrate with canister filters or external filtration systems, heating water as it passes through the filter. They help maintain a more even temperature distribution and prevent fish from coming into direct contact with the heater.
• Undergravel (Cable) Heaters: Popular in planted aquariums, these heaters create gentle circulation through the substrate, improving nutrient distribution for plant roots. However, they tend to be more expensive and less commonly used.
• Electronic and Smart Heaters: Newer heaters feature digital temperature control, remote monitoring, and Wi-Fi connectivity, allowing for real-time temperature adjustments via smartphone apps.

• Stick-on Liquid Crystal Thermometers: Convenient but can be influenced by room temperature, making them less accurate.
• Floating or Sinking Glass Thermometers: More accurate than stick-on types but can be difficult to read, especially in deeper tanks.
• Electronic (Digital) Thermometers: The most precise and easy to read, with some models providing continuous temperature updates and alarms for fluctuations.
• Infrared (Laser) Thermometers: Allow non-contact temperature readings, ideal for quick checks without disturbing the aquarium.

• Air stones for aeration and water circulation.
• Undergravel filters, sponge filters, and internal box filters.

• Mechanical Filtration: Removes solid waste and debris using sponges, filter wool, or fine mesh screens.
• Chemical Filtration: Uses activated carbon, zeolite, and resins to remove toxins, ammonia, and unwanted chemicals. Some media, such as peat, alter water chemistry for species that prefer acidic conditions.
• Biological Filtration: Supports nitrifying bacteria, which break down fish waste from ammonia → nitrite → nitrate. This process ensures a stable, healthy tank environment.

• Undergravel Filter: Common in basic setups, these filters use an air pump to draw water through the gravel, supporting biological filtration. However, they require regular maintenance and are less effective in heavily stocked tanks.
• Powerhead with Undergravel Filter: A powerhead increases the efficiency of an undergravel filter, creating stronger water movement and better waste removal.
• Sponge Filter: Ideal for small tanks, fry tanks, and shrimp tanks, these filters use an air pump to draw water through a sponge, providing mechanical and biological filtration.
• Internal (Submersible) Power Filter: These motor-driven filters sit inside the tank and are suitable for small to medium aquariums. Some models include chemical filtration compartments.
• External Power (Hang-on-Back) Filter: Popular for freshwater tanks, these filters hang on the back of the aquarium and provide mechanical, biological, and chemical filtration. They are easy to maintain and provide moderate water movement.
• Canister Filter: Highly efficient, these external filters provide large surface area filtration, making them ideal for larger tanks. They are quiet and customizable but require occasional maintenance.
• Wet/Dry (Trickle) Filter: These are the best biological filters, commonly used in marine and large freshwater tanks. They maximize oxygen exchange, allowing beneficial bacteria to thrive.
• Diatom Filter: Primarily used for occasional deep cleaning, diatom filters remove extremely fine particles, making the water crystal clear.