# 55w CF Recommendation for 20G Long Planted



## bighurt (Dec 19, 2008)

I have a 20g L planted tank and a few months back upgraded from the standard Allglass hood with a plant light to an open top unit (Odyssea 2X65). I've been running the 14000 k Daylight that came with it. The color isn't that great, but more importantly, the plant growth isn't as good as I want. I have a DIY CO2 setup and dose some liquid ferts.

While I am sure perfecting the CO2 and fertilization will help, the fact remains that the light I'm using sucks. In your opinion, what is the best 55 watt CF that will improve plant growth (and where can I get it)? Assume money is no cost, but if you have a cheap alternative that is pretty good, please provide that as well.

Thanks everyone!
The BigHurt


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## TNguyen (Mar 20, 2005)

I don't know about best CF. But I bought mine from AH supply and it work just fine.


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## jtburf (Jul 23, 2008)

For freshwater planted you really should have the 6700's 

This is directly off AHsupply's website

The Length column provides the approximate length of the bulb itself from the end of the glass tubes to the tip of the base pins. Note that the length of the 55w bulbs varies. For the combined length of a 13w bulb with its GX23 socket, add .5 inches. For the combined length of a 36-55w bulb with our moisture-resistant endcap add .6 inches. For the combined length of a 96w bulb with our moisture-resistant endcap, add .5 inches.

** Bulbs with a Color Temperature of 5500K through 7800K are appropriate for freshwater planted aquariums. There is no practical difference regarding plant growth, but there is an appearance difference. Bulbs around 5500K have a warmer daylight appearance similar to early morning light. Bulbs around 6700K have an appearance more like daylight in the middle of the afternoon under a clear blue sky. The 7800K bulb are just slightly bluer than the 6700K but maintain a balanced, daylight spectrum.

For marine aquariums, you'll want to mix 7800K or 10000K bulbs with Blue bulbs in a ratio of 1:1 or 2:1 or use the Combo bulbs which have one tube that is 10000K and the other tube dark blue actinic. 

For Blue actinic bulbs we provide a description rather than a color temperature so you'll better understand what appearance to expect. Those bulbs called Bright/Medium Blue put out most of their light between 400nm and 500nm. Those called Dark/Deep Blue put out most of their light between 380nm and 450nm. Both have their primary spectral peak at around 420-430nm. Actinism is a property of radiation which, in the visible spectrum, has wavelengths between 380nm and 500nm. 

General compact bulb info:

The Rated Life of a bulb, as supplied by the manufacturer, is an average of how long the bulb will light. About 2% light for 180% of the rated life, about 2% light for 20% of the rated life, though by far the vast majority fall close to the manufacturers' averages. The rated life of most tri-phosphor compact fluorescent bulbs is 8000 to 12000 hours. For an aquarium application, the effective life is usually about 12 to 14 months -- or longer if your total lighting is high relative to the needs of the species in your tank, especially for freshwater setups. 

The Color Rendering Index (CRI) for all 5500K bulbs is 91-92. That's "excellent" in CRI talk. All other bulbs in the 6700K to 10000K range have a good CRI in the low 80's. A common Cool White fluorescent bulb usually has a CRI in the low 70's. That's considered "fair." CRI's below 70 are considered "poor." Note that CRI is irrelevant for marine setups when the aim is to simulate the appearance under many feet of water rather than to simulate the appearance of colors under full spectrum light. Blue actinic bulbs used on marine setups usually have a CRI in the 20's or 30's.

The difference between CRI 92 and CRI 84, for instance, doesn't mean that all colors are rendered with 8% less accuracy with CRI 84. It only means that certain colors that depend on the wavelengths that the CRI 84 bulb is lowest in will be rendered somewhat less accurately. It is likely that the CRI 84 bulb will supply all the wavelengths necessary to render all colors you are interested in very well. That's why a CRI in the 80's is considered "good."

A lumen is essentially a measurement of brightness to the human eye and is therefore very heavily weighted to the middle wavelengths of light that the human eye responds to most readily. As such, this measurement is not very helpful for aquarium applications since the middle wavelengths are the least important to aquarium inhabitants. To focus on lumens can be very misleading. For instance, the 55W 5500K bulb in the chart above has 4200 lumens while the 55W 6700K bulb has 4600 lumens. Yet these bulbs have the same total light output. The 6700K bulb simply has a little more of its output in the middle wavelengths.


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## vancat (Nov 5, 2004)

go with ahsupply- I have their 55CF (single) over my 20g long and the tank does GREAT even without CO2.


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## trenac (Jul 16, 2004)

Welcome aboard 

If you want to go up 10 watts then I would recommend a 65 watt freshwater Coralife fixture. That's the one I used on my 20 long. 

For bulbs you don't want anything above 10000K. There is too much blue spectrum which plants don't use much of. That's more then likely the reason your plants are not doing well.


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## nguyendetecting (Dec 26, 2008)

I agree with the above posts about the light ratings, with a 2x55w fixture you should be doing fine with plant growth. Can you post your lighting schedule and substrate? that might help us find some problem you might have there. Also which liquid ferts and what kind of plants are having problems?


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## nokturnalkid (Feb 27, 2007)

I think that with that light spectrum you are limitng growth. I would definately get something with a lower k rating. Somewhere in the 6500k to 7800k range. Personally, I would go with one light at about the 6700k and the other get the ge 9325k. Before I had that combination, I had all 6700k. I could pretty much grow anything with 4 6700k lights, but things just looked a bit "muddy". After researching, I switched out half the bulbs for the 9325k and it was literally night and day. The growth rate was still there but things just looked crisper. Btw, I was running 4x55watt over a 55 gal.


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