Apogee Instruments Full Spectrum Light Meters & Quantum Sensors are high-end underwater PAR measurements meters that apply the sensor's immersion effect correction factor to the meter readings through firmware. The MQ-510 meter is excellent for all light sources, including LEDs. With the MQ-210, the LEDs post-measurement correction factors need to be applied to achieve accurate readings. The ITC Reefculture PARwise Device is a unique light meter with the ability to measure spectrum. It can be used underwater and in air. It gives you all of the relevant lighting measurements required to make informed decisions.Useful Links:Aquarium Testing RecommendationsIHow to ACCURATELY Test Aquarium Water Article.Related Products: Aquarium Controllers.