T-5 HO 6500k or 10000k any differnce???? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 3 Old 12-06-2011, 08:05 PM Thread Starter
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Question T-5 HO 6500k or 10000k any differnce????

I own a 36 inch nova T-5 HO light fixture with one 10000k ligt bulb and one flora freshwater bulb,but wait I was just double checking and the bulb it self says 12000k and so does the box it came in.The store online advertices it at 10000k.Well any way I think its to bright I know its to bright for my taste.I was wondering if I replace the 12000k with a 6000k or 6500k bulb will it not be as bright as the 12000k bulb.I have no live plants now but plan on maybe getting some later much later.
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post #2 of 3 Old 12-06-2011, 08:46 PM
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10 and 12k will appear more blue, the 6500k more yellow. if you want less light, a single bulb compact flouro would work.
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post #3 of 3 Old 12-07-2011, 12:37 PM
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The kelvin (such as 6500K or 10,000K etc) is the measurement of colour as perceived by us (humans). It has no bearing on the light intensity (brightness) as perceived by the fish and plants. The higher K light may appear "brighter" to us because it is a cooler or crisper white light, as opposed to a warm white (4000K or 5000K etc) which tends to be "softer" in appearance. But all this has nothing to do with the intensity of the actual light, as measured in lumens.

You don't indicate the tank size, so I can't say much about your light setup, but I would think along with onefish2fish that cutting back to one tube might be necessary. Without live plants, light has only one function, to illuminate the aquarium for the aquarist to enjoy the fish. And this should always be the least amount of light necessary to do this. I explain the effects of light on fish here:

The light colour obviously impacts how the colours of the fish and other objects in the aquarium appear. Again without live plants, this is up to your individual taste. Personally, I would avoid excess in either direction (warm or cool) since these will distort the colours and not provide a true rendition. I find the colours of most freshwater fish to be sufficiently varied that having a basic "daylight" light providing a truer rendition of the colour is best. This also happens to be pertinent should you decide on live plants. Tubes with a K between 5000K to 7000K serve this purpose, with those closer to 5000K being warmer or softer than those closer to 700K. Mid-day sunlight is around 6000K I believe.

Any light in the absence of live plants will cause algae. That is not a bad thing, as algae serves the same purpose as live plants, consuming organic nutrients and CO2 and producing oxygen. And any type of normal algae is up to the aquarist. Algae is only "bad" in planted tanks when it attaches to plant leaves and suffocates the leaf and then the plant. So if you are thinking of live plants in the future--which is a very good idea in any freshwater aquarium--you should plan accordingly if you decide to change fixtures. I won't go further into this now.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]

Last edited by Byron; 12-07-2011 at 12:41 PM.
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