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Discussion Starter · #1 ·
I have a 20L a few months old, already done cycling. I bought a 20 inch All Glass Fluorescent light. heres the link:

http://www.petco.com/product/107313/All-Glass-Aquarium-Fluorescent-Single-Tube-Strip-Light.aspx

The back of the fixture says 19 watts but the bulb says 15 watts. So do I have 15 watts or 19? I found out the kelvin rating is 8000K. I'm not sure if this is the right light color for plants.

I want to add another light so I can get into the planted stuff. I just want to run the basic low light plants like java moss, java fern, hornwort and a few grass looking plants.

Since I have an all glass lid, i'd like to get another light that can sit in the glass as well. I haven't been around this stuff enough to know what I should buy to get what I want. Can anyone give me some recommendations? I want a low light tank, but enough light to not be restricted to the bottom five plants. Should I just buy another one of the same lights I already have? That should put me at 30watts/20 gallons. I'm not sure if it is good light for plants. Help?
 

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Couesfanatic,

Your bulb is a 15w. 8000k is just fine for growing plants. Truth be told, all light in the spectrum will be utilized by plants. I had the same question/concerns about lighting when I first started my planted tank and had a Sunpaq dual 10,000k / 420nm Actinic bulb. Any light in the visible spectrum is useful to plants. As light enters water, different wavelengths with different "energies" will penetrate to varying depths. Red light (630-780 nanometers) penetrates only to about 15 meters, while blue light (420-490 nanometers) can penetrate to as deep as about 250 meters. This is why the ocean appears blue.

The best light therefore has nothing to do with what color or Kelvin rating the bulb has. Kelvin ratings are totally and completely meaningless. In fact bulbs are not even accurately rated with the correct Kelvin rating. It's actually a joke. Best light has only to do with what our eyes perceive as an aesthetic. Whatever K rating combination you find pleasing is adequate. Having said that however, note that the human eye is not very sensitive to blue light and they may make the tank appear dim and colors of the plants to be slightly off.
 

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Discussion Starter · #3 ·
So I should get another bulb right? 30 watts/20 gallons should work good?

I'll probably get a whiter blueish bulb if I can. Thanks
 

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So I should get another bulb right? 30 watts/20 gallons should work good?

I'll probably get a whiter blueish bulb if I can. Thanks

If you get another 15w bulb it will give you 1.5w per gallon. The watts per gallon rule is not set in stone and is only a general guideline to get you close. If you put a 5w bulb over a 1 gallon tank, you would have 5w per gallon of light, but I bet there isn't much growing in there. There are many other factors to consider. Such as how heavily planted, water circulation, CO2 injection, nutrient dosing regime, photo period(hours your lights are on), water temp, etc.
 

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Discussion Starter · #5 ·
But as far as lighting I should be ok? I'm not looking to CO2 and all that. I want just a few plants. I have pretty good water circulation right now. I'm not willing to get into CO2, my temp is 76 and I usually run my lights 11 to 12 hours a day.
 

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I'm in a similar situtation as you Cousefanatic. Bought a 20 gallon starter kit with a fixture for 1 15 watt bulb max. I've read 2 watts/gallon is enough to open up your choices by a lot. Seems like you'll be able to reach that fine. I've also heard many comments about growth spurts caused by adding a co2 system.
 

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Discussion Starter · #7 ·
I think i'm gunna buy the same light I have but in a 30 inch. Here is the link:

http://www.bigalsonline.com/BigAlsU.../allglasssinglestriplight30black#ReviewHeader

So 17 more watts should put me at atleast 32 watts/20 gallons. I think this should be ok for my lighting needs. I plan on getting this bulb as well:

http://www.bigalsonline.com/BigAlsU.../cl0/zoomedultrasun6500ksuperdaylightlamp30t8

Its a 6500K Daylight Zoo Med Bulb. I think my 18 inch 8000K 15w bulb and this 24 inch 6500K 17w daylight bulb should be a good combination.
 

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Kelvin is important when selecting tubes. Plants utilise different parts of the spectrum in different ways. The higher the k rating of a tube the more likely you are to get algae problems for a start. I won't go into great detail about it but sufficent to say that you really want to try & get tube/s that are rated between 5-10,000k. Look for lights with large peaks in the red, green & blue parts of the spectrum. Plants photosynthisise most efficiently with green light, then red & last of all blue.
Depth of the tank is what matters when it comes to how much light you need. Watts per gallon is totally irrelevant & is just a very rough guide for popular aquarium dimensions. EG - two tanks can hold 30gal but if one is a 15inch deep standard rectangle & the other is a 30inch deep octogon, they will obviously have different intensity requirements to penetrate enough light to the bottom.
I think you would find that two 18w tubes over your tank would be quite sufficient as it isn't particularly deep. As a side note a general rule when it comes to selecting your plants is the darker green the leaves the more efficent they are at photosynthisis. The lighter green the leaves the less efficient they are at photosynthisis. Meaning that you need less light to grow darker colored plants than light colored plants. You may want to keep that in mind when selecting the plants you wish to use down in the bottom area of your tank.
 

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Kelvin is important when selecting tubes. Plants utilise different parts of the spectrum in different ways. The higher the k rating of a tube the more likely you are to get algae problems for a start.
This is a false statement. Algae is a factor of not enough nutrients and/or CO2. Particularly PO4.Here is a link to a study done by Tom Barr on this subject. http://www.barrreport.com/estimative-index/62-estimative-index-dosing-no-need-test-kits.html
A quick excerpt from the study: 'An important aspect of this method is the knowledge that excess nutrients do not cause algae blooms as so many authors in the past and many today still maintain without having tested this critically in aquariums with a healthy plant biomass. It is a welcomed relief knowing that “excess” phosphate, nitrate and iron do not cause algae blooms.'-Tom Barr
For more on this study you can read the article on what they did and how they came up with their findings.



I won't go into great detail about it but sufficent to say that you really want to try & get tube/s that are rated between 5-10,000k. Look for lights with large peaks in the red, green & blue parts of the spectrum. Plants photosynthisise most efficiently with green light, then red & last of all blue.
Also not true. Light in the green spectrum is the LEAST efficient in plant growth because it is relected by the plant. That's why they are green. The red(promotes flowering) and blue(promotes leaf growth) are the most efficient spectrums for growth. Plants use the same visible light spectrum that we do (wavelengths measuring between 400 and 700 nanometers). That is why you should buy lights that are aesthetically pleasing to you as an individual because the plants will use it. How effective to plant growth the bulbs you choose is another matter entirely. But since they are green, they reflect green wavelengths. The plant can't utilize a reflected wavelength of light as it can other non-reflected wavelengths.
A couple of links for you:
http://aquat1.ifas.ufl.edu/guide/photosynthesis.html
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPS.html
http://en.wikipedia.org/wiki/Photosynthetically_active_radiation


Depth of the tank is what matters when it comes to how much light you need. Watts per gallon is totally irrelevant & is just a very rough guide for popular aquarium dimensions. EG - two tanks can hold 30gal but if one is a 15inch deep standard rectangle & the other is a 30inch deep octogon, they will obviously have different intensity requirements to penetrate enough light to the bottom.
Agreed.

I think you would find that two 18w tubes over your tank would be quite sufficient as it isn't particularly deep. As a side note a general rule when it comes to selecting your plants is the darker green the leaves the more efficent they are at photosynthisis. The lighter green the leaves the less efficient they are at photosynthisis. Meaning that you need less light to grow darker colored plants than light colored plants. You may want to keep that in mind when selecting the plants you wish to use down in the bottom area of your tank.
Dark leaves do take in more light on a 'photon to photon' PAR (photosynthetic active radiation) basis. So as it were, they receive more light. But this does not mean that they are more effecient at photosynthesis. The lighter colored leaves might not take in as much light, but they process what they do take in just fine.
 

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But as far as lighting I should be ok? I'm not looking to CO2 and all that. I want just a few plants. I have pretty good water circulation right now. I'm not willing to get into CO2, my temp is 76 and I usually run my lights 11 to 12 hours a day.
Yes your lighting will be fine. Depending on the amount of ferts you use I would probably step down my lighting period to around 8-10 hours at first. The longer you have the lights on the higher the demand for nutrients by your plants. Start with a shorter photoperiod for 3-4 weeks using the recommended dosing by the manufacturer of the ferts you use. Note the results you get. If no obvious signs of deficiency or algae. Step your photo period up an hour for another 3-4 weeks and see what happens. Every tank is going to have different needs and takes time and experimentation to figure out what your particular tank needs are.

You can use Seachem Excel as a Carbon source for your plants as well. Without the hassle of CO2.:D

I'm in a similar situtation as you Cousefanatic. Bought a 20 gallon starter kit with a fixture for 1 15 watt bulb max. I've read 2 watts/gallon is enough to open up your choices by a lot. Seems like you'll be able to reach that fine. I've also heard many comments about growth spurts caused by adding a co2 system.
Yes, 2 WPG will open your plant options up a bit and the addition of CO2 will cause your plants to have rapid growth. But having said that, there is more to it than that. With faster growth comes the demand for more nutrients. Adding CO2 should cause steady growth, and not a 'spurt', as long as you understand the need for more macro and micro nutrients. If you get a 'spurt' then maybe what has happened is that you added CO2 but didn't increase nutrient levels and over time the plants used up their energy stores and growth came to a halt.
 

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I have a 20L a few months old, already done cycling. I bought a 20 inch All Glass Fluorescent light. heres the link:

http://www.petco.com/product/107313/All-Glass-Aquarium-Fluorescent-Single-Tube-Strip-Light.aspx

The back of the fixture says 19 watts but the bulb says 15 watts. So do I have 15 watts or 19? I found out the kelvin rating is 8000K. I'm not sure if this is the right light color for plants.

I want to add another light so I can get into the planted stuff. I just want to run the basic low light plants like java moss, java fern, hornwort and a few grass looking plants.

Since I have an all glass lid, i'd like to get another light that can sit in the glass as well. I haven't been around this stuff enough to know what I should buy to get what I want. Can anyone give me some recommendations? I want a low light tank, but enough light to not be restricted to the bottom five plants. Should I just buy another one of the same lights I already have? That should put me at 30watts/20 gallons. I'm not sure if it is good light for plants. Help?
Have you found a light yet? For what you want to grow, http://www.bigalsonline.com/BigAlsU...6/cl0/coralifefwt5aqualightdoublestriplight36 could be nice or a 65 watt pc fixture. It's a little more than what you are looking at, but worth it in the long run. I'd also recommend getting the legs so you can go opened topped or to raise the lights. It is cheaper to buy them together shipping wise. What are your plans as far as co2? Excel, diy, pressurized or none? This will also determine the lighting you'll want to get.
 
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