How much PAR is too much?

[DrHank]

I know that this may be a controversial subject but I'm wondering how much PAR does my tank really need and can I over do it? I'm currently running four 250W 14 K Hamiltons on M58 ballasts. From what I've been able to determine, each bulb is producing just a touch over 200 PAR. That is a far cry from a Ushiro 10K which may produce as much as 900 PAR on the right ballast.

So where is middle ground? to further complicate matters my tank is a Mixed Reef and I really don't want to change it. I'm going to increase PAR (gradually) but should I go to 300, 600, I don't think 900?

Let me know what you think and remember that there aren't any wrong answers I'm looking for opinions.

 

[prow]

good subject, definitely not a ya or na thing. chech this out, its no too old. Feature Article tell me what you think, i found it very interesting and it lead me to look into each specific coral reactions to certain PAR levels i was most interested in. all and all with our type of lighting i would say yeah you can have too much. but then again the photoperiod plays its role, a few less hours may not produce the effects.

 

[prow]

kinda cool huh. for your tank because no testing has really been done with LPS and softies. photochemical quenching and non-photochemical quenching should be somewhat controlled with your photoperiod.

 

[DrHank]

I would agree that it is an interesting article. Also I would agree that you can overdo it as far as very high par over extended periods. I'll also say that tends to lead me to the conclusion that the longer the photoperiod is the lower the PAR level should be. It only addresses one specific SPS but implies that it may be the same for related species.

For my purposes (Mixed Reef) it tends to make me think that PAR values around 300 might be best if I'm using MH exclusively (8+ hours a day). Higher values say 600 would possibly be desired for a more SPS dominated reef although the photoperiod should probably be reduced and supplemental lighting used during non peak times.

 

[mps9506]

Keep in mind the PAR levels will vary depending on where it's measured in your tank. Not only by depth but where it is in relationship to your bulb. Reflectors vary in how well they spread the light and how intense the light is in different spots. You can use this to your advantage by knowing what areas of your tank have higher levels of PAR.
I think saying I have bulbs with 300 PAR isn't specific enough to be conclusive on what is good for your specific tank. Reflectors, light spread and depth all have a big deal with this as well. You may have a bulb that has 600par at 12 inches of depth right under the bulb, but 20 inches under the bulb it might be 1/4 that, and 5 inches to the left it might be even less.

 

[cheeks69]

IMHO and experience yes you can have too much and it's one of the reasons I don't use XM bulbs anymore.

As has been mentioned extended photoperiods with the same intensity for 8-12 hours is unnatural and although corals properly acclimated can usually adjust that's not always the case. The last couple of years I have switched to higher Kelvin bulbs which generally speaking have lower PAR and my corals have reacted much better.

 

[DrHank]

Excellent points. Now you have me thinking of the merits of shorter photoperiod on the MH and supplemental lighting with T5s or PCs. My 155 bow has an Aqualight fixture with MH and PCs and the few soft corals I have in the tank seem to be doing wonderfully.

Seems as though no matter what we do, we can't match mother nature.

 

[cheeks69]

I have in the past reduced my MH photoperiod to 6 hours with no noticeable impact on color/growth of my SPS corals, currently it's 8 hours MH and 10 hrs actinics.