Did I buy a bad light?

[CatatonicBug]

I made a bit of a mistake... I think.

I wanted to swap out the fake plants in my tank and go for real ones, so I went to the LFS, and bought 2 clumps of plants, that are supposed to get up to 72 inches tall (my tank is over 3 feet deep).

I was told that I needed to replace my lightbulb, since it had been over 2 years since I had done so. I was at the LFS, and found the bulb section. Not knowing anthing about lights, or what the ratings meant, I went for the highest K number I could find, thinking that would get me really bright light... I have since found out that plants actually like a certain K rating, and I may have purchased the wrong one. Will the 18000k bulb I bought kill my plants?

 

[Glenc]

That light won't kill your plants, they will still grow, they just may not grow as well as they would with a lower K rated bulb. Most planted tank people use a K rating of between 5500k and 10000k. I use a mix of 6700k and 10000k. It's personal prefrance,whichever is more pleasing to your eye. In general, lower K ratings mean a more yellow colour, higher the K gets you will see more of a blue/white light. Plants will use whatever light you give them, they typically just do better between 5500k and 10000k. Maybe see if you can exchange the light for one with a lower K rating

 

[Karegg]

It's personal prefrance,whichever is more pleasing to your eye. In general, lower K ratings mean a more yellow colour, higher the K gets you will see more of a blue/white light.

That's pretty cool. I personally think I'd rather have the blue/white, but how much more expensive was the 18000 K over, say, a 10000 or lower?

 

[p3purr]

As Glenc said, an 1800k bulb won't hurt. I'd use a lower k for your other bulbs.

How many bulbs do you have on the tank? A 3ft high tank would need a lot of light. How long and deep (front to back) is the tank? What type of light/lights do you have. A NO fluorescent won't penetrate that deep. I don't think a VHO would do it either.

 

[CatatonicBug]

Other bulbs?? I only have room for one. The tank came with a light fixture with one 18" bulb in it. Te measurements of the tank are thus:
30" tall X 20" wide X 18" deep (front to back)

What is a VHO?

The 18000K was about $10 more than the 10000K bulb. I do kinda like the look of it, but my wife doesn't. Maybe once the white haze goes away, I will be able to tell better.

 

[p3purr]

Other bulbs?? I only have room for one. The tank came with a light fixture with one 18" bulb in it. Te measurements of the tank are thus:
30" tall X 20" wide X 18" deep (front to back)

What is a VHO?

Oh, I read your original post to say that the tank had a height of 36" :

I went to the LFS, and bought 2 clumps of plants, that are supposed to get up to 72 inches tall (my tank is over 3 feet deep).

Regular fluorescent bulbs are:
NO = normal output
HO = high output
VHO = very high output

The bulbs are NO unless otherwise listed.

Your tank is a 47 column (20x18X30). One 18" T-8 fluorescent bulb is 15 watts which works out to .32WPG. Low light plants take at least 1WPG, more on a deep tank. You'd need more than 50 Watts on the tank, probably 75-100 watts minimum. A 2x36 watt Bright Kits from AH Supply (36 or 55 watt Bright Kits) might work but a 1x36 and a 2x36 would work much better.

I would consider going with a tank that's shallower for plants.

 

[CatatonicBug]

Yeah, sorry for the measurement inaccuracy. I was just guessing the first time.

Thanks for the math. I really like having information like that. I am actually starting another small tank for plants, but I really want to have real plants in this tank. Maybe if I save my pennies, I can upgrade the lighting one day.