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tyler12345 04-12-2008 07:53 PM

Purchasing a new light... Help please!
Currently, I have a 38 gallon tank with a 17 watt light on it. I am going to purchase a new light and plants maybe tommorow. How many watts/whatever would I need to grow a plant that needs a lot of light? Just something so that I would be limitted to what plants I can buy/grow.

herefishy 04-12-2008 07:59 PM

As you didn't say shat type of bulp your current fixture uses, I will assume it is a fluoresent bulb. Look for a bulf that is in the range of 6700K-8500K. It alaso should be a full spectrum bulb. Some lamps such as FloraLux, and others, will do the job. Wattage has nothingto do with plant growth, so don't listen to any nonsense associated with it.

If you are having to buy a new fixture, look for a compact fluorescent fixture or on the uses T5 bulbs.

tyler12345 04-12-2008 08:16 PM


fish_4_all 04-13-2008 01:51 PM

Put your tank dimensions in here to figure out how many watts of lighting you in the correct spectrum and good lumens. This will give you different light levels for your tank. If you go above moderate then you run into possibly needing at least DIY CO2 to prevent major amounts of algae.

Remember, junk lighting will not matter if you put 50 or 400 watts over the tank. It won't grow plants. High CRI (85+) Kelvin rating of least 5500 but lower than 10K. And the higher the lumens the better. This is why T10 is better than T12, T8 better than T10 and T5 better than T8. Each time you step down in number you get more lumens and intensity for the size. Might take 3 bulbs for T5 instead of 2 for T12 but the output is much higher, the size fo the bulb is smaller and they are more efficient.

okiemavis 04-13-2008 04:19 PM

Ooh, very cool link! I now believe I have high lighting, not moderate lighting on my tank :D

fish_4_all 04-13-2008 04:55 PM


Originally Posted by okiemavis
Ooh, very cool link! I now believe I have high lighting, not moderate lighting on my tank :D

Okay, I am little confused now. 17 watts over a 38 gallon can not be high lighting. Did you get a new fixture? Just to make sure you are reading it right, how long and wide is your tank? Even with a 10 gallon tank, 17 watts isn't even close to high light.

Recommended Wattage Lighting Level
Compact Fluorescent
56W VeryHigh
43W High
28W Moderate
14W Low
T8 Fluorescent
54W VeryHigh
41W High
27W Moderate
14W Low
Hagen T10 Fluorescent
72W VeryHigh
54W High
36W Moderate
18W Low
T12 Fluorescent
76W VeryHigh
57W High
38W Moderate
19W Low

kritas 04-14-2008 12:26 AM

Wattage is only to determine the amount of power used.
What you are looking for is the Kelvin rating. (eg 6700K)

My 10 gallon tank has a 15W bulb hanging over it, meaning its super efficient, and the Kelvin rating is at 18000K's! I don't even understand myself how its that high but it is.(and BTW, can someone with more experience tell me if 18000K is too bright for my 10 gallon?)

fish_4_all 04-14-2008 01:26 AM

tyler12345, to answer your question, you need to get right around 130-150 watts of proper lighting to grow anyhting you want without worrying about light. Go with the chart from gotdns. Find high light for each type and decide what lighting type you want to use. Get the lighing that you need that gives you the Wattage and Lumens you need. The Lumens calculations are broken down on the website. This will give you all you need to know to grow anything. You will want to get CO2 running as soon as possible. DIY is ok for the tnak but anyhting over 25-30 gallons really needs pressurized. If you don't want to mess with CO2 then go with moderate lighting or lower and buy plants accordingly.

The Kelvin rating is nothing more than the color rating of the bulb. True direct sunlight is 5500K or there abouts. For the purpose of aquarium plants, 6500K is the most used and most reliable Kelvin rating. It is extremely important to have the right but useless by itself. As for 18,000K lighting, to do with the brightness of the bulb. Only the actual color of the light.

It doesn't matter if you have the perfect Kelivin rating, the best CRI (Color Rendering Index) and the highest lumens for a single bulb. If you do not have enough wattage to provide enough lumens then all of it means nothing.

Until I see a better chart or better explanation I will use THIS web site to determine what I need. I was produced by 4 top of the line fish keepers and is endorsed but at least 2 plant experts.

When it comes down to it, all the truely matter is Lumens. If you have enough lumens from the wattage in the right spectrum and a high CRI then you will grow the plants you want to. If you don't you won't!

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