Light w/gal Question

[drum4jc]

Hi folks,

After reading Carl's articles numerous times, I bought two of the 15 watt compact fluorescent lights at 6700K and I'm wondering what the effective "watts per gallon" would be for my 26 gallon tank. I.e., would the higher lumens etc give it a higher effective rating than the (30/26) = 1.2 w/g?

[Carl]

Nov 27, 2009 23:16:17 GMT -5 drum4jc said:

Hi folks,

After reading Carl's articles numerous times, I bought two of the 15 watt compact fluorescent lights at 6700K and I'm wondering what the effective "watts per gallon" would be for my 26 gallon tank. I.e., would the higher lumens etc give it a higher effective rating than the (30/26) = 1.2 w/g?

Yes since these watts per gallon "rule" (which although still useful as a starting point as we are here is very out of date since it misses other important measurements of useful light energy).

Since this "watts per gallon" is based on older lights that traditionally produce 40 lumes per watt and these basic CFLs produce 60 lumens per watt we can multiply your 1.2 by1.5 which = 1.8 watts per gallon for comparison purposes.

Here are the main considerations:
• Watts per gallon,
• Lumens per watt, PAR (often easiest determined by Kelvin output),
• Lumen focus
• PAR
• Useful Light Energy (not wasted in yellow/green light spectrum that green plants and zooanthellic algae reflect)
• Output in relation to bulb length (this is where T2 and LED excel).
• Lux, I generally only consider this parameter in deeper Reef and occasionally deeper planted freshwater aquarium to determine if I am getting the proper light where it needs to be.

We already have addressed the first two, the forth area is PAR, so here here it needs to be an apples to apples comparison, however since these are approx. 6500K temperature which roughly produces the highest % of PAR as compared to many other light sources we might assume another 25% increase in efficiency making your number measured in watts per gallon 2.25 for your 26 gallon.

Unfortunately in Lumen Focus and wasted energy we cannot add to our numbers as this is not a strength of these bulbs (LED and to a lesser degree T2)

Since these are short CFLs we cannot add in the area of bulb length either.

So I would assume approximately 2 + watts per gallon for your tank which would make these fine for low to possible medium light plants.

If you need more light, consider T2s (which have more lumens per watt and less wasted energy)

Carl

[drum4jc]

Thanks Carl. I knew the higher lumen output would help crank that up a bit, but I wasn't sure how to get a ballpark figure. I have low and moderate light plants in the tank and they seem to be doing fine, except that my java ferns don't look too good. So that made me wonder if they are getting too much light. They look a little blackened. I noticed that you said the root ball should not be in the substrate, so that could be an issue too. I hate to have them floating around...

(In case you're wondering, I'm using the Wonder Shells, Seachem buffers, Excel, Seachem liquid ferts and a pellet fert, and a DIY CO2.)

[Carl]

My experience with Java Ferns is that they do not need too much extra care, so although I am not telling you to avoid using the products you named, I am saying that often reasonably good lighting (which these CFLs represent) and a reasonable amount of bio available nutrients/minerals is all you may need.

I know babygeige and Suzie Q have had excellent results with Java Ferns, so maybe they might have some good input if they are available over the long weekend

Carl

[babygeige]

I have a 30 gallon that i kept java fern in. I upgraded my light to a 96 watt and the guy at the LFS warned me that the java fern didn't like too much light. I left them in to see what would happen and he was right. All of my plants started to grow better except for the java fern. I ended up removing them and putting them in a different tank, where they have been doing very well.

If you don't want the java fern floating around, try tying it off to a rock or piece of wood. Of you can put the roots in the gravel, just be sure to keep the rhizome above ground. Try doing this to see if they perk up before you give up keeping them in the tank.

[drum4jc]

Hey, thanks for the quick responses. I'll make sure the rhizome is exposed. I'll also see if I can move them to a more shaded place in the tank too.

If they don't work out, I can get more Wendtii's. Mine are doing great in there.

[babygeige]

Wendtii's are great plants! I forgot about them. I used to have bronze ones in my tank, but I had a nasty black beard algae outbreak and lost them. I might get some more of those some day!