Aquarium lighting guide – Your most common questions answered

Right lighting is essential for maintaining a healthy ecosystem, not only during setting up your aquarium. It supports plant growth, regulates the biological clock of fish, and enhances the visual appeal of your tank. But it also raises many questions: What kind of lighting should you choose? How many hours a day should it be on? Does the light spectrum really matter? In this guide, we answer the most frequently asked questions about aquarium lighting – whether you’re just starting out or you’re an experienced aquarist.

We all need light #

Lighting plays several crucial roles in a thriving aquarium:

• It supports photosynthesis in aquatic plants, ensuring their healthy growth.
• It regulates the day-night cycle of fish, helping reduce stress and promote natural behavior.
• When properly selected, it helps prevent excessive algae growth.
• It enhances the colors of fish, plants, and decorations, making the aquarium visually stunning.

Poorly chosen lighting can stunt plant growth, stress out your fish, and even trigger algae blooms. Choosing the right aquarium lighting system is key to success.

Aquarium lighting guide – types of light source #

There are many types of lighting on the market, each with its pros and cons:

1. Fluorescent tubes (T5, T8) #

Once a staple in fishkeeping, they’re now being replaced by more advanced solutions. While they offer even lighting, they consume more energy and have a shorter lifespan than newer technologies.

2. LED aquarium lighting (widely regarded as the best) #

The most popular option today – and for good reason:

• Energy-efficient
• Long lifespan (up to 50,000 hours)
• Adjustable intensity, color, and spectrum
• Excellent for plant growth thanks to a wide light spectrum

3. HQI and metal halide lamps #

Mainly used in marine aquariums or large planted tanks with demanding species. These provide intense, high-temperature light but are expensive, heat up significantly, and consume a lot of energy.

Choosing the best light for your aquarium type #

Your lighting needs will vary depending on the kind of aquarium you have: 

• Community tanks (fish + basic plants):
  Go for LED lights with a color temperature of 6500–8000K and a power output of 0.3–0.5 watts per liter. Examples of plant species that grow in the very low to low lighting bracket include Anubias, Cryptocoryne, Java fern and various mosses.
• Planted tanks (Aquascaping):
  These require intensive lighting (0.8–1 watt/liter) with specialized LED lights that allow spectral adjustments. Plants like Rotala, Glossostigma, and Hemianthus cuba demand strong light and CO₂ supplementation.
• Marine aquariums:
  Light spectrum is key – especially the blue range (8000–10000K and higher). Coral and reef organisms need specific lighting, often at 1–2 watts/liter, with advanced control systems.

Color temperature – what do Kelvin ratings mean and how it can help with growing aquarium plants? #

Color temperature, measured in Kelvin (K), affects photosynthesis, aesthetics, and aquarium health:

• <4500K – warm, yellow light. Enhances red tones in fish but less effective for plant growth.
• 5500–6500K – neutral white, similar to daylight. Great for general use.
• 6500–8000K – optimal for planted aquariums (best light for growing aquarium). 
• >8000K – cool, bluish light. Mostly used in marine tanks to support coral health.

Some advanced LED fixtures let you mix red, blue, and white LEDs to tailor the light spectrum to your aquarium’s needs.

PAR and PUR – what do these terms mean? #

• PAR (Photosynthetically Active Radiation): The amount of light available for photosynthesis.
• PUR (Photosynthetically Usable Radiation): The portion of PAR that plants can actually use.

Different plants have different lighting needs. Shade-loving species like Cryptocorynes can thrive with lower light levels, while high-demand plants like Glossostigma require intense, well-balanced light. Without proper CO₂ and nutrients, too much light can fuel algae instead of plants.

Aquarium Lighting – How many hours should aquarium lights be on? #

The ideal lighting duration is 8–10 hours per day. Longer periods (over 12 hours) may trigger algae growth, while shorter durations can slow plant development. A timer ensures consistency and prevents overexposure. Many advanced LED systems also offer sunrise and sunset simulations to promote natural rhythms.

Light intensity and aquarium depth #

Light loses intensity as it travels through water – the deeper your aquarium, the more powerful the lighting should be. For tanks deeper than 40 cm, choose lights with higher intensity to ensure it reaches the substrate. Proper lamp placement and reflectors help distribute light evenly and maximize efficiency.

Aquarium Lighting: Lumens – is brightness all that matters? #

Lumens measure brightness, but high lumen output doesn’t always mean better plant growth. Consider:

• Standard aquarium LEDs: 3000–4500 lumens
• High-end lighting for aquascaping: Up to 21,000 lumens

More important than lumens is having the right spectrum for your specific plants and fish.

Preventing algae growth – what to watch out for #

Too much light, excessive photoperiods, or an imbalance in nutrients (like CO₂ and fertilizers) can cause algae outbreaks and increase aquarium maintenance requirements. To avoid this:

• Limit lighting to 8–10 hours a day
• Avoid direct sunlight
• Regularly monitor water parameters and nutrient levels
• Keep lighting fixtures clean to maintain performance

Other factors to consider in tank lighting #

• Light distribution – Avoid dark spots by ensuring uniform coverage.
• Reflectors and hoods – Help direct light into the tank, increasing efficiency.
• Maintenance – Clean your lights regularly to prevent dimming.
• Observation – If you notice poor plant growth, stressed fish, or algae, lighting could be the culprit.

Final tips for right aquarium lighting #

1. Match lighting to your tank type and inhabitants in order to keep healthy aquarium.
2. Opt for LED lighting, as it is regarded as the best light, for energy savings, durability, and flexibility.
3. Use a timer to maintain a consistent lighting schedule (8–10 hours/day).
4. Adjust lighting conditions – color temperature and spectrum – based on the needs of your plants, fish, or corals.
5. Keep an eye on your aquarium – lighting is critical, but it works best when balanced with proper CO₂, fertilization, and care.

As you can see, lighting is very important and we hope this guide helped you with better understanding if the lighting options. For more expert advice and tips, check out our other articles on the blog!