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Discussion Starter #1
I know this is going to sound weird but, is there a difference between having a 4 bulb fixture or a 2 bulb fixture? It seems the 2 bulb ones are alittle cheaper but I want to get a good one. I will need to get a 48" fixture. Any thoughts on that? I will add one thing, The 2 bulb one did'nt have seperate on/off switches, which I think is a good idea.
 

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Having more bulbs is a real benefit. There are different methods to approaching a planted tank (e.g. low tech, high tech) and so depending on which method you'd choose, the amount of lighting would be different. So, if you start off with low tech, for example, and don't need so much lighting, then you could use only two of the bulbs on the four bulb fixture. Then, if you decide at some point to go a bit more higher tech, you could make use of the additional two bulbs, either all of the time that the lights are on or having two bulbs on one timer and the others on another timer. This would enable you...so long as you dose CO2 and apply fertilization properly, to keep a wider variety of aquatic plants, including red and pinker plants for a great variety.

I'd suggest that you get the four bulb fixture and when you're choosing a particular fixture, look for one that has individual reflectors for each of the bulbs.

Another alternative would be to have two fixtures with two bulbs each and place them a bit away from each other on the top of the tank so that you get a broader coverage, but that's up to you and not critical if you get the fixture with the individual reflectors.
 

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Discussion Starter #3
Thanks Avi, sounds good to me. Where in Westchester are you? Know of any planted tank clubs close by?
 

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^^^ mister obvious :D

make sure we're talking about t5 (27W) vs t5 HO (54W) for each bulb.
The light fixture you'll get DEPENDS on the size of your tank and if you want to go hi-tech or low-tech
 

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Discussion Starter #8
Ok, let me clarify this. Sounds like you guys think I'm an idiot. I was asking if there was a benifit to haveing a 4 bulb fixture over a 2 bulb one. Just starting out with live plants, I want to make sure I get what's best for them. As I said, 2 bulb fixtures seem cheaper but there seems to be alot more options with a 4 bulb system, as well as more light output. Thats what I was asking opinions on. I will need a 48" fixture and I plan on keeping medium and low light plants in a 75g tank that's 24" deep. I was told, in another thread, to go with T5 NO, 4 bulb fixture.
 

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You want to do some simple math....

75 gallons X 3 watts/gallon (could go higher to 5 but that is overkill) = 225 total watts

Most 48" bulbs are 54 watts...

225 watts/54 watts/bulb = 4.17 bulbs

So ideally you will want to go with a 4 bulb unit. I hope this helps.

(a two bulb unit will provide just under 1.5 watts per gallon, yes it will still work but would not be ideal)
 

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You want to do some simple math....

75 gallons X 3 watts/gallon (could go higher to 5 but that is overkill) = 225 total watts

Most 48" bulbs are 54 watts...

225 watts/54 watts/bulb = 4.17 bulbs

So ideally you will want to go with a 4 bulb unit. I hope this helps.

(a two bulb unit will provide just under 1.5 watts per gallon, yes it will still work but would not be ideal)
Watts are not like fertilizers. You don't put watts into the water, have them dissolve, and make light throughout the volume of water in the tank. Watts are a measure of the power a electrical device uses. If you substitute an ordinary resistor for the lights, you can put 1000 watts over the tank and it will be totally dark - except for the infrared from the heated resistor.

Watts per gallon means about as much as Kelvin degrees per gallon - nothing at all. By coincidence, if you use T8/T12 bulbs, without good reflectors, you can use the power of the light fixture divided by the volume of a standard shape tank to get reasonably close to what light is needed. Trying that with T5HO light fixtures, with excellent reflectors, is not a meaningful way to pick a light.
 

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He's new and asking a simple lightning question. The answer I gave him is a fairly easy guide to buying a lightning fixture. We aren't talking about resistors we are talking about lights.

Obviously, it's not perfect since you can leave lights on for various lengths of time , different bulbs, height of bulbs and not to mention type of plants/fish in the tank. But if he buys a fixture in the range I quoted he will be able to do most everything with his tank without running into issues. It's easy to adjust time lights are on ($10-$20 timer from Lowes), height of lights, type of plants, etc...buying a new light fixture isn't practical to everyone.


There is no such thing as degree Kelvin....it's just Kelvin.
 

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Are you planning on getting a CO2 system? If not, dont get more than 2x54w T5HO or algae WILL take over your entire tank. I have a Nova extreme 2x54w on my 75G and if i go more than 2 days without excel algae starts taking over.
 

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2x54W without CO2, 3 or 4x54W with CO2.

If you aren't going to use CO2 and just want low tech stuff, there is no need for T5HO or even T5NO. A 2x32W T8 shop light is $20 at Lowes. Bulbs are super cheap.
 

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If you are planning on medium and low light plants you definitely do not need more than 108 watts of T5 HO light over a 75 gallon. Even at that light level you will probably have to add Excel or CO2 and there is no reason you cannot also grow plants that are considered "high light" plants too. Other than faster growth/more trimming/maintenance and a much faster rate of algae growth if you mess up there is not a lot to be gained by running 216 watts of T5 HO lighting over a 75 gallon tank.

The old WPG rule comes from the days when people were using T8/T12 bulbs. PC and particularly T5 HO have really changed the way we need to look at light. These forums are filled with posts from people who bought T5 HO fixtures based on the WPG rule (and worried they would not have enough light) and then had significant problems with algae/stunted plant growth. Massive amounts of light can help to grow out a tank quickly if you really know how to control it and prevent algae but long term tons of light really isn't necessary to grow healthy plants.
 

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Discussion Starter #15
Wow. Thanks for all the advice guys. So, if I want to go with 4x 54w T5 HO I NEED CO2. And, I could even go with some "high light" plants because the WPG ratio is way different with T5 bulbs. If I chose to go low-tech (no CO2) I could probably stick with the 2x 32w bulbs I have, possible add some suppliments, and be able to grow the low to medium light plants I wanted. To much light (ie. 4x 54w T5 HO) and no CO2 will cause a massive algea outbreak. Just out of curiosity, why does CO2 dampen the algea growth? I thought it would help it, like it does the plants.
So, did I understand all of that right? If so, I guess my choices are high or low tech, with CO2 or without. Right?
 

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It seems to me that you are asking if you should have two 100W bulbs, or four 50W bulbs. If I had to choose between using a single ballast that supports two 100w bulbs, or four 50W bulbs, I would go with the 4 bulb solution. You can have much more even lighting tank with four bulbs and not have as many shadows. The only reasons I wouldn't use four bulbs is if the 4 bulb reflectors would get in the way too much, or if there's a substantial cost difference between the bulbs.
 
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