40 watts enough for 10 gallon?

Watts per gallon is an outdated form of measurement for a reef tank. It really depends on the livestock you are trying to keep and the type of light being used. (T5's, power compacts, Normal Output lights) If you aren't trying to keep corals, or are only looking for soft corals like some leathers and mushrooms, 40 watts of normal output over a 10 gallon should be fine.
 
The light is actually two t12 2700K bulbs. I'm not trying to grow any hard corals just get some purple algae and soft corals growing.
 
I agree but the 2700k isnt gonna cut it. find a couple 10000k bulbs instead.@ 4watts a gal. the softies will love it.
 
I agree but the 2700k isnt gonna cut it. find a couple 10000k bulbs instead.@ 4watts a gal. the softies will love it.

Why do you need such a high K.

Chlorophyll_ab_spectra.png


It looks like the chlorophyll will absorb red and blue light relatively well. Does the blue light just make the fish feel more at home?
 
You'll need a more broad spectrum bulb to get the most out of the lighting. You'll want to be able to excite various chlorphylls and a 2700K bulb won't really do that. Beyond that, photosynthetic reef animals are adapted to higher kelvin light. Try to aim for at least 6500K (the rating of sunlight at ~1m)--you can go higher, but that really boils down to aesthetic preference.
 
The higher the bluer and it does promote some growth but its not good enough like above said.

You can do the simple mix of 10k and 20k.... or 14k but I am not sure they make bulbs 14k for your fixture ...if you can get your hands on 14k you get your white and blues out of that spectrum. So you dont lose the look you get from the bluer spectrum.

Most people I know do like the bluer bulbs to bring out color..and some corals are deep in the tank types would benefit from the high K spectrums... but most of your growth benefits will come in being more broad... Lots of sps tank users go the happy med 14k some try to go full 10k or lower...closer to 6.7k the better for coral growth on some feedback I have read before.

Now messing up in the past I had 20k hallides and they did not do the job...soon as I put on a 10k...did I see growth and better look to my corals over all health.

So far in my new tank the 14ks are doing very well as a friend with a 100g sps tank suggested going. I so far am very happy with going 14k. The sps in my tank are showing lots of growth and new branching ...I couldn't be more satisfied.
 
I'd go with a T5 setup. Similar wattage with greater output for photosynthetic organisms. The light you chose (GE, I'm assuming) will not be sufficient if you want photosynthetic corals.
 
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