Aquarium Lighting Calculator
Created by: Natalie Reed
Last updated:
Calculate the optimal lighting intensity for your aquarium in lumens and watts. Get PAR estimates, photoperiod recommendations, and fixture sizing based on tank dimensions, depth, and whether you're growing plants, keeping fish, or maintaining a reef tank.
Aquarium Lighting Calculator
AquariumCalculate optimal lighting intensity, wattage, and photoperiod for planted, fish-only, or reef aquariums
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What is an Aquarium Lighting Calculator?
An Aquarium Lighting Calculator helps determine the appropriate light intensity, wattage, and photoperiod for your tank based on its dimensions, depth, and inhabitants. Proper lighting is essential for plant photosynthesis, fish health, and preventing algae problems.
This calculator considers your tank type (planted, fish-only, or reef), water depth, and lighting goals to recommend lumens, PAR levels, and daily light duration. Whether you're growing demanding carpet plants or maintaining a simple community tank, proper lighting calculations prevent common problems.
Aquarium Lighting Formulas
Lumens Required:
Total Lumens = Tank Volume (liters) × Lumens per Liter
Watts per Gallon (LED):
Low light: 0.5-1W/gal | Medium: 1-2W/gal | High: 2-3W/gal
Light Intensity Guidelines:
• Fish-only: 15-25 lumens/liter
• Low-tech planted: 25-35 lumens/liter
• Medium planted: 35-50 lumens/liter
• High-tech planted: 50-75+ lumens/liter
Understanding PAR for Aquariums
What is PAR? Photosynthetically Active Radiation (PAR) measures light energy usable by plants for photosynthesis in the 400-700nm spectrum. Unlike lumens (human-perceived brightness), PAR directly indicates plant-usable light.
PAR Levels by Tank Type:
• Low-tech planted: 30-50 PAR at substrate
• Medium planted: 50-100 PAR at substrate
• High-tech planted: 100-150+ PAR at substrate
• Soft corals/LPS: 75-150 PAR
• SPS corals: 200-400+ PAR
Depth Matters: Light intensity decreases with water depth. A light providing 100 PAR at 12 inches may only deliver 50 PAR at 24 inches. Deeper tanks require more powerful fixtures.
Frequently Asked Questions
How many lumens per gallon do aquarium plants need?
Low-light plants need 15-25 lumens per liter (57-95 per gallon). Medium-light plants need 25-50 lumens per liter (95-190 per gallon). High-light demanding plants need 50+ lumens per liter (190+ per gallon). These are guidelines - actual needs vary by plant species and tank depth.
What is PAR and why does it matter for aquarium lighting?
PAR (Photosynthetically Active Radiation) measures light usable by plants for photosynthesis, in the 400-700nm wavelength range. PAR is more accurate than lumens for plant growth. Low-light tanks need 15-30 PAR, medium 30-50 PAR, and high-light planted tanks need 50-100+ PAR at substrate level.
How long should aquarium lights be on each day?
Most aquariums do well with 8-10 hours of light daily. Planted tanks may benefit from 10-12 hours with CO2 injection. New tanks should start with 6-8 hours to prevent algae. Use a timer for consistency - irregular lighting stresses fish and promotes algae growth.
Does tank depth affect lighting requirements?
Yes, significantly. Light intensity decreases with depth - a 24-inch deep tank needs much stronger lighting than a 12-inch tank to achieve the same PAR at substrate level. Deep tanks may need 2-3x the wattage of shallow tanks for similar plant growth.
What color temperature is best for aquarium lights?
6500K (daylight) is ideal for plant growth and natural appearance. 8000-10000K enhances blue tones, popular for reef tanks. Warmer 5000K lights can work but may promote more algae. Many hobbyists use combination fixtures with multiple color temperatures.
LED vs fluorescent vs metal halide for aquariums?
LEDs are most efficient, longest-lasting, and produce less heat. T5 fluorescents offer good spread and are cost-effective. Metal halides provide intense light for deep tanks but generate significant heat and use more electricity. LEDs have become the standard for most applications.
How do I know if my aquarium has too much or too little light?
Too much light causes algae blooms, especially green water or hair algae. Too little light causes plants to stretch toward light, lose lower leaves, or grow pale. Fish hiding constantly may indicate overly bright lighting. Adjust duration and intensity based on these signs.
Do fish-only tanks need special lighting?
Fish-only tanks need minimal lighting - enough to view fish and maintain their day/night cycle. 0.5-1 watt per gallon or basic LED strips are sufficient. Avoid overly bright lights which stress fish and promote algae without plants to consume nutrients.
Sources and References
- Planted Tank, "Understanding PAR in Planted Aquariums", Aquatic Plant Central, 2024
- Reef Lighting Research, "Coral PAR Requirements Guide", Marine Depot, 2024
- Aquarium Co-Op, "Aquarium Lighting for Beginners", Educational Series, 2024