Which T12 bulb is better for plant growth? - The Planted Tank Forum
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post #1 of 3 (permalink) Old 04-30-2013, 11:29 PM Thread Starter
Algae Grower
Join Date: Apr 2013
Location: Long Island, NY
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Thumbs down Which T12 bulb is better for plant growth?

I currently have hydrocotyle japan and marimo balls growing in my 65gal. Would it be better to use a 3100k 1900lumen 40watt T12 bulb or a 6500k 2900lumen 40 watt bulb? & Why? They are both the GE brand bought from lowes
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post #2 of 3 (permalink) Old 05-01-2013, 01:10 AM
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Location: Chicago
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The 6500k bulb would be much better for plant growth. This is because plants really only use light from the 5000k-10000k range and the 3100k isn't even in that range. 6500k is known as the sweet spot in terms of plant health and growth, so that would be your best option.

Now, the other problem is the wattage of your lighting. It is recommended to have at least 1wpg for a planted tank, and you have about 0.60wpg. Now, i dont know if the marimo moss balls need much light, but i know the hydrocotyle japan (a.k.a pennywort) needs low to medium lighting, which you have very low light so i think it will probably slowly die off or just barely hang on without much growth at all. The best option for you to do is to get at least 1wpg by either buying another one of the fixtures you have, getting a cheap dual t8 shoplight at lowes, or getting a cheap dual t5 aquarium lighting fixture like the odyssea dual t5 for $45.

Good Luck!
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post #3 of 3 (permalink) Old 05-01-2013, 07:40 PM
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This is the only time "WPG" can be used for a relatively safe rating of lighting: when using T12 bulbs.

Plants use light from all spectrums.

On my tank, I'm running 2xT8 6500K bulbs and 2xT8 3500K bulbs. Plant growth is excellent (including the supposedly impossible Madagascar Lace plant).

However, be aware that if you elect to increase your lighting, you may need to start dosing CO2 and ferts to avoid algae. Too much lighting without supporting plant life and growth will give algae the leg it needs to take over.
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