View Full Version : Importance of Light Meter

10/19/2016, 06:42 AM
This article is to demonstrate the importance of have an accurate PAR meter to hand when keeping a coral system. But not just PAR also how useful PUR is and what it is.

Our office system is still in its infancy and coral placement at this time is important as much as in a mature system when adding new live stock. Get the light setting right or wrong is 100% linked to how successful that new coral will be.

So lets start with some basics around a new tank set up. The tank here is just over 200 gallons, with a water depth of 23" taking into account sand bed thickness and water height to the rim of the tank. On this tank the chosen lighting is the NEW Ecotech Radion G4 Pro. The lights are 9" from the water surface, The water is suffering from a new syndrome bacterial bloom which will have some affect on any light reading. The Seneye light meter will play a role in readjusting output once the bloom has cleared.

Ecotech Radion G4 Pro where the most suitable choice as they are probably the only light I know of that the manufacturer puts massive effort into making sure the light truly has the ability to grow corals. Coral Lab is a perfect example of this, more details of Coral Lab can be found on their website.

from the photos here you will see the Seneye Reef monitor that is connected in this instance to the Seneye Web server (all screen shots are from the seneye webpage uploads from the unit in the tank) has been placed with the light meter which is on the back of the seneye device next to a new addition in the tank.



Most LPS corals do best in a PAR of 100-200. From the below screen shots you will see the output is bang on where I would want it. Further reading shows the PUR at 77%, this means 77% of the PAR output is usable for growth. Other measurements across the same depth of the tank were taken to make sure other LPS were not in any hot spot, however with the use of Radion G4's this is little of concern as their output is very uniform. Another screen shot below shows the current Radion settings which are at factory set 14K and at 100% output.

So how does this differ from other light meters? The Seneye Reef comes with a proven and accurate light meter that stands up against units that price in above $1000! take into account the Seneye Reef as a stand alone is $199. of course you then get the added benefits of pH, Temp, NH3 and NH4, monitoring plus relative O2 and also water depth alarms.

Furthermore the Seneye light meter functions are not just limited to PAR, in its arsenal is LUX and Kelvin, but also PUR.

So what is PUR?

The part of the PAR spectrum that is used by photosynthetic cells is called PUR photosynthetic usable radiation. As a seneye measures both spectrums and PAR can give a good idea of the % of PUR in a PAR value.

PUR stands for Photo-synthetically Usable Radiation. It is not a scientific term, like PAR, but can be more useful regarding aquaria as different photosynthetic species (plants, anemones, corals) have different PUR levels, though they may all be within the same PAR. Essentially the PUR is a more focused term describing the specific PAR levels used by each species.
Still confused? Ok PUR is in raw form a reading of usable (growing) light, so the better the reading the better the growth at that reading point. This is a fantastic tool for the average hobbyist that wants to see if their lamp is set at a light level to create the best growing environment. And this is where SENEYE not only differ but provide a very affordable option for measuring your lighting output.

How can I check? A useful device for reef tank keepers - Seneye Reef
PAR and PUR are things that reef tank keepers should be aware of. If not actively monitoring your lights, it would still behove you to know about how PAR affects coral, and which PUR levels your corals need, so informing your choice of lights at purchase.

You can use a visible light spectrometer to check the PAR levels of lights, though this would only allow you to make light readings from outside the tank. In order to ascertain the PAR levels within the tank, you will need a specific light monitoring system (such as the one incorporated in the Seneye Reef device) allowing you to take readings underwater and if necessary at different levels of the tank to establish which areas are most suited for corals.

Here is a great link to guide you as to what levels of light different corals require.


For more information about Seneye contact Premiums Aquatics directly one of the USA's largest stock holders.