PAR

[Guest alex wlazlak]

what is PAR? ive been noticing alot of talk about it latly. also, are PC's even good? i saw that new t5 thread and im gelous now . im going to be doing a 120g eventually and i already have 2 36" PC 96 watt fixtures, and seeing how good the t5s are now, could i mix em up? maybe throw 1 t5 in the front and back of the tank, then the PCs, and maybe even 1 t5 in the middle...?

[Folta]

PAR = Photosynthetic Available Radiation.

 

It's the 'current best guess' as to a way to measure how 'good' a particular light is for providing what corals need.

 

 

You can mix and match lights, so to speak, if you want. Many people (including what I'll be doing on my 180 gallon) have VHO actinics with MH's.

 

It might just be more of a hassle than its worth, to save those lights. Isn't your 120 4' long?

[Guest alex wlazlak]

yeah. but it is hard to get them like sentered andto not have any "dead" spaces. without having water and everything in the tank its also hard to see where there isnt light and where there is. i was testing out the lights the other night and it turns out the one was all srewed up and it didnt light the whole thing and looked like it was going to blow up or somthing, so now i need an extra bulb :( . lights arejust so darn expensive and to buy new ones that have high wattage is going to be hard.

[lmeyer]

PAR = Photosynthetic Available Radiation.

 

It's the 'current best guess' as to a way to measure how 'good' a particular light is for providing what corals need.

 

And now we know about as much as we did before Alex asked the question Folta, I'm not throwing daggers, just expressing the challenge of the hobby. Now I know what PAR stands for, actually already did from Borneman's excellent book, Aquarium Corals. The problem is assuming that I have a relibable PAR meter (I don't, but could get one), how do I know the appropriate PAR for my corals. I've yet to see any documentation on that subject. Its sort of like adding iodine to our tank, there is lots of anectodal evidence that iodine (or more light) is good, possibly necessary, but very little hard science. Borneman identifies the area on a reef a coral is most likely to be found (slope, fore slope, back slope, lagoon, etc) and gives some ideas about peak PAR, but I have yet to see anything that really lays it all out. Anyone else seen documentation along the lines of Euphillia ideally receive between x and y PAR. Crocea clams should receive ...???

[traveller7]

It is unlikely that we have enough power to properly duplicate the sun created PAR available at any depth less the 30ft on the reef with artificial bulbs.

 

That stated, we only need to provide the level of PAR required for the specimen to near saturation. At some point photosynthesis "shuts down" and the critter goes into the dark cycle process and further lighting is "un-used".

 

Saturation point varies based on the critter, specimen size, other available dietary sources, etc.

 

Based on what I have seen, most scientific literature related to lighting do not deal with the types of measurements we can duplicate and we are left with anecdotal evidence to estimate requirements.

 

If you want an opinion:

 

quite a few softies and LPS can go from NO to low MH

quite a few SPS can go from VHO to high MH

quite a few clams can go from VHO to MH (VHO possible for derasa,squamosa, hippopus)

quite a few anemones can go from VHO to high MH (MH for magnifica and gigantea)

 

quite a few anemones can go from VHO to high MH (MH for magnifica and gigantea)

[ErikS]

To "sort of" answer the PC question. PC's put out a decent amount of light.....but...because of the shape they are very poor at delivering it into the tank. Meaning the shape causes a great deal of re-strike/light loss. Single bulbs like VHO's & T5s are much better able to deliver the light into the tank.