Spectrum of radiation at different depths:
The spectrum of radiation changes as we move from the surface to the deeper parts of the ocean. The red and yellow wavelengths are absorbed within the first few meters, while green and blue wavelengths penetrate deeper. At depths greater than 10 meters, only blue wavelengths are visible. Therefore, it is important to choose a light source that has a spectrum that matches the natural light at the desired depth.
Types of lighting:
There are different types of lighting available for marine reef aquariums, including metal halide, T5 fluorescent, LED, and hybrid systems. Metal halide lighting has been the most popular in the past, but it has high energy consumption and emits a lot of heat. T5 fluorescent lighting is more energy-efficient but does not provide enough PAR for SPS corals. LED lighting is the most energy-efficient and customizable, with the ability to adjust the spectrum and intensity of the light. Hybrid systems combine different types of lighting to provide the best of both worlds.
PAR levels for different types of corals:
PAR (Photosynthetically Active Radiation) is the amount of light available for photosynthesis. Different types of corals have different PAR requirements.
SPS (Small Polyp Stony) corals require higher PAR levels, ranging from 250 to 450 (μmol/s/m²), while LPS (Large Polyp Stony) corals and soft corals require lower PAR levels, ranging from 50 to 150 (μmol/s/m²). It is important to measure the PAR levels in the aquarium and adjust the lighting accordingly to ensure optimal growth and coloration of the corals.
However, the required PAR amount can vary depending on the coral species, reef depth, and other environmental factors such as water quality and coral population density. For example, SPS living in shallow waters near the surface of the sea require a very high amount of light, while those living in deeper waters can tolerate a lower amount of light. It is also important to consider the depth of your tank, as PAR decreases as light penetrates deeper into the water. This means that corals and other photosynthetic organisms at the bottom of your aquarium will receive less PAR than those at the top. To ensure that all of your corals receive sufficient light, it may be necessary to adjust the placement or intensity of your lighting.
There are several tools available for measuring PAR in marine aquariums. Here are a few options:
1. Apogee MQ-200 PAR Meter: This is a popular PAR meter among aquarium hobbyists. It has a range of 0-2000 µmol m⁻² s⁻¹ and comes with a handheld sensor and a data logger. Apogee MQ-200 Quantum-Meter
2. Seneye Reef Monitor: This is a monitoring system that measures PAR, as well as other parameters such as temperature, pH, and ammonia. It has a range of 0-2000 µmol m⁻² s⁻¹ and connects to your smartphone or computer for easy data tracking. Seneye REEF V2 – aquarium monitoring system
3. Neptune Systems Apex AquaController with PMK PAR Monitoring Kit: This is a more advanced monitoring system that includes a PAR sensor, as well as other sensors for measuring temperature, pH, and ORP. It has a range of 0-2000 µmol m⁻² s⁻¹ and connects to your Apex controller for easy data tracking and control. Apex – PMK :: PAR Monitoring Kit
There are also various online calculators available online to help you determine the PAR levels in your reef tank. Here below one example :
1. Coverage/PAR for current control point : Aquaticlog Keep in mind that these calculators provide estimates and should be used as a guide. It’s always best to use a PAR meter to get the most accurate readings for your specific tank and lighting setup.
Choosing the right lighting for your tank is essential for the growth and sustainability of the corals. Understanding the spectrum of radiation at different depths, types of lighting, and necessary PAR levels for different types of corals can help aquarists make informed decisions. It is important to measure the PAR levels in the aquarium regularly and adjust the lighting accordingly to ensure optimal growth and coloration of the corals.
If you want to document yourself, this is the book for you: The Manual of Marine Invertebrates: A Comprehensive Guide to the Care and Husbandry of Invertebrates in a Home Aquarium:
The book includes a section on light and PAR measurement.
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