Re: To Watt or not to Watt

[Bill Wichers <billw at waveform_net>]

>Choice #1) Coralife Power Compact hood with 2 - 96 watt bulbs (1 -
>10,000k & 1 Actinic).  192 watts divided by 27 gallons = 7.11
>watts per gallon!!  Am I looking at problems with having this much
>watts per gallon?
>[Choice #2) Coralife Power Compact hood with 1 - 96 watt bulb. (50/50 -
>Half 10,000k & Half Actinic).  96 watts divided by 27 gallons =
>3.55 watts per gallon.  Am I too limited with plants I can grow with
>this little watts per gallon?
>Choice #3) Helios Power Compact hood with 4 - 36 watt bulbs. (2 - 7100k
>Daylights & 2 - 12,000k Actinics).  144 watts divided by 27
>gallons = 5.33 watts per gallon.  I know 4 - 5 watts is optimum and
>this is probably my best choice using that standard.

I think you have been talking to too many REEF people and too few PLANT 
people. There are VERY DIFFERENT "optimal" setups for each. You don't need 
any actinic lights at all for plants, and will probably be better off 
without them for both growth and appearance. Also, 10000K is way too high a 
color temp for a planted tank unless you really want it to look bluish. 
Even many reef people consider 10000K to be a high enough color temperature 
that a reef tank lit with 10000K bulbs doesn't need supplemental actinic 
lighting.

Over a 27g tank your ideal light setup would probably be two 36w PCF 
lights, for a total of 72 watts. You would be able to grow a lot of stuff 
with just a single 55w PCF light, but I don't think it would be long enough 
to evenly light the entire length of the tank. The two 36w fixtures should 
fit better and provide more complete illumination -- the primary factor 
between the pair of 36w fixtures and the single 55w fixture would be 
providing EVEN LIGHTING over the tank and not just providing more wattage. 
You do want to avoid large shadow areas.

>I am going to be using C02 injection.  The Coralife has a built-in
>fan and ballast which I'm not very fond of, but I like it's style better
>than the Helios.  I guess they both have good & bad.  So
>the real question . . . is 7.11 watts/per gallon too much, and is 3.55
>watts per gallon too little if I don't want to be too limited with what I
>can grow?

Yes, 7.11 watts/gallon is way too much light. I have grown batches of green 
water using much less light than that. 3.55 watts/gallon would be useable, 
but is still very far over on the high side. Most plant people use 
somewhere in the 2-3 watt/gallon range, and that is with the efficient 
lights like PCF and MH. That 4-5 watt per gallon number you quote sounds to 
me very close to what is usually recommended for reef tanks when using MH 
lighting. It's way too much for plant tanks.

BTW, Coralife tends to be among the most expensive aquarium supply brands, 
and they don't offer enough over many of the cheaper brands to be worth the 
expense, IMHO.

Get yourself a 55w PCF or a pair of 36w PCF lights, and use a bulb in the 
5000-6700K range. Don't use any actinic lights at all. You'll be very 
pleased with the results. Put the money you save into a good substrate like 
Flourite, and get a decent CO2 setup. Both will help growth far more than 
higher light levels.

         -Bill


>Thanks for any advice.
>
>
>Mike Gothreaux

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