# Best lighting for 20 gallon 24L x 13W x 16H



## fishstein (Dec 12, 2005)

I'm about to pick up a 20 gallon acrylic tank this week. All the lighting systems I made up to now were for 2 ft and 4 ft bulbs, which are very standard. Which lighting solution would you suggest for a tank of this size? 

The tank doesn't have a canopy but I can make one quite easily from wood. A 24 in. bulb won't fit nicely inside a neatly fitting canopy. The tank comes with a light that is probably a CF light from what I can tell from the picture (buying used), as the light fixture is about 2/3 size of the tank. The light that comes with the tank may be powerful enough for my use, as I intend to keep this tank with Seachem Excel and no CO2.

I like to use high efficiency bulbs like T5, T8 and CF, and use high efficient reflectors so that I can use less bulbs and save energy and heat. I also like to be able to have at least 2 timers each controlling 50% of the lights, though again one bulb will probably be sufficient for this tank. Any suggestions for lights/fixtures?


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## fishstein (Dec 12, 2005)

So looks like the Giesemann 24W T5 will fit the 20 gallon canopy, as it's only 22.2 inches long. With an efficient Tek II reflector, even with one bulb I may need to use CO2. That could be quite a bit of light for a 16 inch tall aquarium with 2.5 inches of substrate.

I'll wait to see what kind of light comes with the tank, hopefully it will be a fixture/light I can use.


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## jcali10 (Jun 17, 2007)

It's pretty standard, 2 ft light fixtures normally fit on 2 ft tanks. So any 24 inch fixture should work, be it CF or T5. The bulbs are not 24 inches long. The fixture is. Maybe I'm missing your point. 

For an organic CO2 tank, 4-24W or 4.8 WPG of light is enough light to grow anything, insufficient CO2 may be a problem. Never had that much light on a tank, not to mention an Excel only tank. 

(2) 24 watt T5 lights would provide 2.4 wpg, this is in the medium light range. You should be able to grow a lot of different plants. Since you will be using organic CO2, I think this option would be more appropriate. 

With 4 bulbs, I can see where you may want to go with a midday burst. If you use 2 bulbs, one timer should be sufficient. 

What is the best light? I'm not sure. I know what is expensive. How much are you willing to spend? Are you thinking only fluorescents?

Regards, 
Joe


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## stuckintexas (Aug 12, 2008)

2x24W giesemann T5HO middays would be really good lighting on that tank. I think you could grow anything...not sure how well excel will work with that much light. as far as being able to independently control the lights, that would be expensive as you would need two ballasts, two timers. bottom line, its a great light choice but if you dont have proper carbon source you might be growing algae out the wazzoo.


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## fishstein (Dec 12, 2005)

jcali10, 2 T5s with Tek II reflectors is actually way more light than you would think. The reflectors push tons more light down, so you can use less bulbs. If the projection of light from the reflector is wide enough, I'm 100% sure I could get away with 1 22 in. T5 bulb with a 24 in. Tek II reflector on the 20g. 

Given the fact that the tank is not deep, it's possible it could still require CO2 even with one bulb + reflector. If I stick with a Seachem Excel only regimen, 1 T5 with Tek II reflector will certainly be more than enough light.

The tougher thing to figure out is how to handle light for the 135 gallon setup, which is a 24 in. deep tank. It is possible with 3 inches of substrate that I could get away with either 2 80W bulbs with Tek II reflectors (which would leave the ends not perfectly covered), or 4 39W bulbs with Tek II reflectors. For both tanks, I'm not going for fastest growth, but rather stable steady growth of a wide range of colorful plants. I want to be able to grow red plants, but don't care to grow the most light-hungry species. I was able to grow beautiful red plants with 4 32 watt T8 bulbs with reflectors on our 75 gallon.

BTW, I never buy fixtures, I've always retrofitted my own lights, reflectors, end caps, etc., which is much cheaper.


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## jcali10 (Jun 17, 2007)

I agree with your point about reflectors, high quality reflectors will put more light on your tank. I've read about restrike too. I better understand where you are coming from now. I'm not trying to be critical of your ideas, I sincerely was just trying to be helpful. 

It seems to me like you have abandoned the watts per gallon rule, which is simple and useful because people can easily relate to wpg when discussing their tank paramaters. So you've adjusted the WPG rule to take into account better reflectors, where 1.7 wpg over a 75G tank is equivalent to what exactly? Have you calculated that? or are you just making a judgment based on past experience, which is fine also. 

Apparently you already know from personal experience, what works for you regarding light intensity and organic CO2 supplementation. 

For your 135, regarding light penetration and depth, I think if the light is 30 inches or more from the substrate, you may need to consider stronger light, such as metal halides. I'm just guessing here. You'll have to do some research. There are some very lengthy, technical, and in-depth posts on light parameters, that provide everything you always wanted to know about light but were afraid to ask, written by folks that are actually knowledgable in that field. 

BTW, I only buy fixtures. 

When planning a new set up, we always want to get it right the first time. I understand that it is important to make the correct purchases. Mistakes can be costly. That's why we share our thoughts and look for feed back. So good luck.

Regards, 
Joe


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## fishstein (Dec 12, 2005)

Hi Joe,

I never took your post as criticism - every bit of experience and knowledge contributed makes any project better. I learn a little something from every post, and there is so much yet to know. See my post - there's not a critical line in there. I was only thinking out loud about light requirements. I can't stand it when posters in any forum flame people just for offering their experience or disagreeing. I've learned things even from reading the newest newbie post.

I've never done any calculations, just basing off my experience. See the post I just wrote on what I learned from my 75 g going from T8 bulbs to better T8 plant bulbs to mylar in my hood to DIY 98% reflective parabolic aluminum reflectors. I was getting high quality growth at far less than standard WPG guidelines, saving electricity and reducing heat output - something all of us should be interesting in.

In discussing the 135 g light requirements in that thread, some posters with experience with T5 and Tek II reflectors think that I could even get away with 3 T5 80W bulbs with Tek II reflectors, staggered across the midline of the tank.


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