Worried about light shock

[JVJordan]

I've just changed out OLD 250 watt Radiums for new XM 10k bulbs. Sanjay's site shows Radiums at 55 PPFD and XM 10ks at 115 PPDF.

I've cut the photo-period from 5 hrs to 3 hrs and raised the lights about 4 inches. Any opinions on likelihood of shocking the corals with too much light? Specifically worried about the Acros & encrusting monties.


Thanks!

 

[aNDoN]

if the corals you are worried about are anchored and you're afraid they are gonna bleach still try this:

I add screens to the top of my tank in layers when adding new corals. Normally 5 layers. Then every 3-4 days I remove a layer. If you did this, then slowly moved your lights down, then slowly increased your photo period back to 5, you should be fine.

The par may be a little higher with the 10K, but since you aren't increasing intensity the steps you have done should deter any mishaps.

 

[toothman]

can you just raise the light off the tank a bit. 10k are much brighter

 

[sirreal63]

I just went through this earlier this year, and the par isn't just a little higher, it's double, so yes you do need to account for this. The screen works well, as does raising the lights and cutting the photoperiod. I raised the lights, moved the acro's as close to the sand as possible and still bleached. If you can raise them higher, I would. If you are running very low nutrients, you can offset some bleaching by raising nutrients slightly, which I don't normally recommend but it does help the zooxanthellae if they are not starved for nutrients. I have done this successfully several times but you may have more algae to contend with for a little while. In my case the Valonia exploded with growth but no other nuisance algae appeared.