Temperature And Par

[Crazy fishes]

Just a few quick questions regarding PAR and the temperature of bulbs in halide fixture. Is it possible to increase available PAR by choosing a cooler temperature bulb? I would have thought so as the sun is about 6700K and therefore our 10,000-20,000 K bulbs have peak frequencies above that of the sun. Also why when you 'over do it' with lighting (i.e lighting too powerful) do corals go brown. Is that brown colouration due huge amounts of zooxanthelles in the tissue? I am really interested as I sold a frag of my frogspawn to one of the many LFS and it has gone a 'manky' brown colour. It is about three foot under 3x 250W halides (I believe 14,000K) at a water depth of many two to two and a half feet. I can tell you that the rest of the colony is under a 150W 14,000 K halide at a foot away from the halide, 6-8 inches from the water surface. I have noticed an increase in the brown colouration along the tentacles but brilliant fluorescent green tips. I am curious as to why the frag I sold is so brown with no green tips? It really looks horrible, certainly not attractive to buy but is it reversible??

Regards

Joe

 

[SkiFletch]

Yes, it is possible to increase PAR by selecting different lamps. Switching more towards "True" 6700K will increase PAR for sure, but remember, color temp is just a best-guess as to the actual spectral output of the bulb. There's no science behind color temp. Usually it's a good indicator but not always. For example, XM 10K halides have high PAR, 20K have less PAR, but their 15K model has the worst PAR out of all of them... And in 175watt SE, the Iwasaki 15K lamp will put out more PAR than most 10K lamps and even some 6700K. Sadly there's not much data on Flourescents.

"Browning out" can happen for a whole bunch of reasons. Most commonly, it happens when chemistry is poor, or light is low. In this case, the organism allows more brown zooxanthellae to grow to combat stressors. However the opposite high lighting can also be troublesome to a coral. Hitting them with a lot more light can cause the coral to grow defensive pigments in its skin to try and keep it from being burned. It's basically like getting us humans getting sunburn. In both cases, if ideal conditions are met, this is certainly reversable. It may take significant time on the order of months, but corals can recover from browning out.

 

[Crazy fishes]

Thanks Ski for the reply most appreciated. Another question slightly off the subject I am having a problem with this type of algae. I can do a water change and within a few hours the glass is misted with the stuff. It is really fine and easily wiped from the glass where it looks almost powdery. I checked the chemistry which is all as stable as ever; nitrate and phosphate are unrecordable with Salifert kits. Do you think it could be phytoplankton? I remember a while back when I got my first clam, the deresa, I tried something with this 'brine shrimp food' to encourage a more ecological system. Nothing happened until about three weeks ago now it grows super fast??

Any ideas

Regards

Joe

 

[SkiFletch]

Could be, tough to say without a pic, which I'm sure would be hard with an algae like that. Perhaps a pic series?