What lighting should you choose for your aquarium?

For many, aquarium lighting seems like a given. A well-lit tank immediately catches the eye and adds charm to any interior. More importantly, proper lighting enhances the colors of your fish and supports plant growth making it essential for a healthy aquarium environment. Because lighting plays so many roles, selecting the right setup requires understanding both the technical options available and the specific needs of your fish and plants.

The day and night cycle in an aquarium

Maintaining a regular day and night cycle benefits your fish’s overall well-being by keeping their biological clock in sync. Irregular or overly long lighting periods can stress fish, as they aren’t able to rest properly. Yes, fish do sleep though in a very different way than we do.

Aside from the visual appeal, light is also crucial for plant growth. Healthy aquatic plants contribute to a balanced ecosystem by releasing oxygen and absorbing excess nitrogen and phosphorus. Lighting, alongside nutrient-rich substrate and water, is a key factor for plant development. Without adequate light, only low-light species like mosses or certain water trumpets can survive and even they need some access to ambient daylight to thrive.

That said, sunlight is not suitable as a primary light source for aquariums. Its unpredictable intensity and angle throughout the year can promote algae blooms and cause significant temperature fluctuations. Artificial lighting, on the other hand, lets you control intensity, color, and duration—essential for maintaining balance.

What light sources are used in aquariums?

Fluorescent lighting

Fluorescent lamps are glass tubes filled with mercury vapor and argon, with tungsten electrodes at each end. When voltage is applied, a discharge between the electrodes emits ultraviolet light, which is converted into visible light by a phosphor coating inside the tube. The phosphor layer determines the light’s color, quality, and intensity. Aquariums typically use two types of linear fluorescent tubes: T8 and T5. While T5 lamps (with a slimmer diameter) are more powerful and efficient than T8s, they are also more expensive. One downside of fluorescent lighting is its declining performance over time bulbs need replacing every 6 to 10 months, especially in planted tanks.

Fluorescents are now being widely replaced by energy-efficient LED lighting. Still, if you have an older tank setup, many manufacturers offer LED lamps with adapters that fit T8 or T5 sockets allowing you to upgrade without changing your aquarium hood.

High-pressure discharge lamps (HQI)

Metal halide (HQI) lamps are high-pressure discharge bulbs containing a mixture of noble gases, mercury vapor, and halide salts (like fluorides and iodides). Light is generated by an electric discharge between two electrodes, which heats the gases and causes the halides to emit light. By tweaking the gas mixture, manufacturers can produce various color temperatures.

However, HQI lamps generate a lot of heat and require proper housing for safe operation. Since they also emit UV radiation, they should never be used without a protective glass cover that blocks harmful rays. While more expensive than fluorescents, HQI lamps are highly efficient and maintain their brightness longer. They’re best suited for large or deep aquariums (over 60 cm), including marine and planted display tanks.

LED lighting

LEDs have become the standard in modern aquarium lighting. While initially more expensive, they offer long-term savings due to low power consumption and durability not to mention their sleek, stylish design. LED systems can last for years without needing replacement, making them a hassle-free option for most aquarists.

Conclusion

The best aquarium lighting combines the right intensity, spectrum, and color temperature with energy efficiency. It should also avoid raising water temperature especially important in summer months for tanks with enclosed lighting. Don’t forget: all electrical components must be installed safely and according to regulations. If you’re unsure how to handle it, consult a qualified electrician.

Dawid Krótki