- when to change old lamps and how many of a multiple to change at one time

- will the new coral I'm buying suffer light shock in my tank and how can I avoid that

- is my new or current light canopy in the optimal position and are my lamsp close enough, too far or too close to the water

- does this window or greenhouse glazing offer enough or too much sunlight?

- does the light I'm using have not only enough intensity, but enough PAR(!) to keep my reef corals and creatures alive

There are many more challenges we encounter that could readily be addressed with the use of a PAR meter. A keyword search of the Internet will reveal other authors such as Sanjay Joshi and Dana Riddle of Riddle laboratories with published articles on this issue. I like and recommend a PAR meter for all non-casual aquarists. Most of us have many thousands of dollars invested in our reef systems. A couple hundred dollar investment in a light meter can make a huge difference in the success and health of the aquarium. Several members of this board own the brand below and like it well. I agree FWIW:

http://www.apogee-inst.com/bqm_spec.htm 

Re: which to choose, you must ask yourself:

are you measuring electric lamps, sunlight or both?

Do you want a water proof sensor or not?

My advice is to get all of the above if you can afford it my friend: Model QMSW-SS

(and to be clear - I do not know these people or this company, I have never taken a free product sample or any sort of comp from them... and MD does not sell these units presently (nor have plans). It's simply a good brand/product that stands on its' own merit. Hence my recommendation.)

.

Anthony Calfo

Sorry to drag up an old thread, but how would you use one of these light meters?

How would you know when a lamp needed changing? what % drop in intensity are we looking for? what sort of intensities do we want for different corals etc?

Thanks in advance

Keith

I cannot tell you what exact reading to target when I do not know what species you are growing, if you are doing monocultures, etc.

For starters though... do take a peek and see the PAR reading you get outside on a cloudy day. Then compare that to the PAR reading you get under artificial lights that have been uised to keep/grow corals well. Very simple but telling experiments.

Are you at least getting 100-300 PAR?

For more science information (like how to convert lux )... the Net is an amazing tool Please do be resourceful my friends rather than wait for simple answers/enabling.

If it helps you... of the many informative threads and info I have collected or built for you/aquatics friends, you will see a very nice science URL in my recommended links in the sticky atop this forum called "Fav links...":

http://science.howstuffworks.com

* the name says it all... "How Stuff Works" 

.

Anthony Calfo

It is a principal aspiration in my life to be a teacher/mentor... and not an enabler. Its tough to finesse that line sometimes without seeming grumpy or brusque But you have done well by me/us, my friend. Thank you for digging/learning and sharing.

.

Anthony Calfo

Anthony Calfo

I just talked with a biologist friend of mine and he says that there is no direct conversion between lux/par. PAR measures photosynthetically active radiation only, so how does it take into account the rest of the light, it doesn’t, so how can it be used to derive a measurement of that light (non PAR light)? What is your opinion on this?

Thanks,

Ben