how much light do sps really need?

[klepto]

The more light the more you stress your sps . The key factor here is if your par is good 5 to 6 hour of day light is fine any more will stress the zooxanthellae in the sps causing lake of color and slow growth. If your par is low then more light time is needed like 8 to 10 hours a day. So more light in sps is not a good thing at all. Its called photoinhibition

What are you basing this on? I know plenty of successful reefkeepers that run photoperiods far beyond 5-6 hours without any issues.

Photoinhibition "...occurs at all light intensities and the rate constant of photoinhibition is directly proportional to light intensity. Some measurements suggest that dim light causes damage more efficiently than strong light.[11]" http://en.wikipedia.org/wiki/Photoinhibition

I think your suggestion of; more light leading to increased photoinhibition is flawed.
Photoinhibition bleaching usually occurs alongside tidal changes which subject wild corals to drastically higher PAR than usual. Unless the aquarist is rapidly changing the PAR that their corals are recieveing, then I don't see how this term comes into play.

If properly acclimated to high PAR, most reef building corals can tolerate very intense lighting.

PAR values on wild reefs usually far exceed those in aquaria.

 

[sahin]

I agree with Mammothreefer; I had several frags bleached out completely due to one or more factors. They turned COMPLETELY white in colour. Much worse than Mammothreefers photos. Corals can managed for upto 6 weeks in this bleached state. - The source of that info is from a BBC documentary on the Great Barrier Reef (presenter is a Marine Biologist). Just like it was explained on the documentary, the corals will expel all the Zooxanthellae due to conditions which cause severe stress. They can survive upto 6 weeks without the Zooxanthellae. During this time if the conditions become well again they will "pickup" free floating Zoox from the water and colour up again. The loss of Zooxanthellae isnt death of the coral. As long as the tissue hasnt stripped off and the polpys (ie the animal) is present, the coral will soon colour up. I have had corals go from bone white to colouring up again in a matter of less than a month.

 

[iwishtofish]

Hmmm....

This tri-color acro of mine has been bleached for months, and I've almost given up on it. It has PE, though, and might even have grown a small bit. I can't put it lower without snapping it off - might just do that as an experiment, to see if it browns up.

(I apologize to the OP if this has strayed too far off-topic)

 

[Ostentum]

I am surprised noone has chimed in with this yet. Most SPS reach their photoperiod saturation at about 6-6.5 hrs. Can you grow corals at 4 yes, can you grow them at 10 yes, the data is out there that shows both, are 4 and 10 the most effective and efficient, probably not.

 

[MammothReefer]

Hmmm....

This tri-color acro of mine has been bleached for months, and I've almost given up on it. It has PE, though, and might even have grown a small bit. I can't put it lower without snapping it off - might just do that as an experiment, to see if it browns up.

(I apologize to the OP if this has strayed too far off-topic)

I would leave it as is. I didn't move mine, it just took time. I also try to feed a little more and while I have no proof that my corals eat oyster feast. I figure if I can at least have a chance to prolong there existence while they recover by supplying them with nutrients from another source it can't be a bad thing. Specifically if you are seeing PE.

 

[MammothReefer]

I am surprised noone has chimed in with this yet. Most SPS reach their photoperiod saturation at about 6-6.5 hrs. Can you grow corals at 4 yes, can you grow them at 10 yes, the data is out there that shows both, are 4 and 10 the most effective and efficient, probably not.

I was waiting for somebody to do so I know the numbers are out there. I just didn't recall what they are. I'm keeping mine at 4 for a combination of reason but I also decided to add the t5's back on the time, so now I have my halide (over the frag tank) running for 4 hours, and then my t5's running for 4 after that. Thanks, 6-6.5 sounds about right althuogh I swear there is some advanced aquarist article out there with all this info.

 

[OneReef]

Bleached is not dead. Dead is dead. Ha