# Watts per gallon



## robert2191 (12 Oct 2015)

Im upgrading my aquarium to about 480l but i need to buy lights for it i want it a planted aquarium would 4x 54w t5 be enough for that size aquarium or more 
I know you can work out how many watts per gallon but not sure how
Thanks


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## Martin in Holland (13 Oct 2015)

Watts per Gallon is not accurate, you should be measuring PAR, but a PAR meter is very expensive and almost no one has one, so what to do?
First, T5 light are very powerful and I'm sure 4 x 54W will be to much, myself I have 1.5 (parts are covered) T5's running above my 300 liter tank and it seems more than enough.
 As guide you can use this....


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## robert2191 (13 Oct 2015)

Martin in China said:


> Watts per Gallon is not accurate, you should be measuring PAR, but a PAR meter is very expensive and almost no one has one, so what to do?
> First, T5 light are very powerful and I'm sure 4 x 54W will be to much, myself I have 1.5 (parts are covered) T5's running above my 300 liter tank and it seems more than enough.
> As guide you can use this....



Thanks for your reply, sorry don't really understand that graph  I normally just keep the lights what come with the tank but this tank I'm getting  don't come with them 



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## foxfish (13 Oct 2015)

I would think 2 or maybe 3 would be sufficient but if you can make them individually switchable 4 would be ok.
2x T5s the lenth of the tank was (not so long ago) the standard recomedatsion for co2 injected tanks up to 55 cm deep.


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## ian_m (13 Oct 2015)

robert2191 said:


> Thanks for your reply, sorry don't really understand that graph


The graph is used to roughly determine if your lighting setup will mean a low tech, medium tech or high tech. Going higher tech means more frequent water changes, carefully controlled CO2, high levels of fertiliser but much faster growing plants and if it goes wrong (algae, melting plants etc) it all goes very very quickly.

So using 4 off T5 tubes and 20 inches deep tank (for instance) gives a PAR reading of 65PAR x 4 = 260PAR which is in the monsterously high light region...so algae & ,melting plants here we come.

Yet two tubes is 130 PAR which is high, but manageable as a high tech tank.

We don't know your tank depth, so just guessing at what tech level 2,3 or 4 tubes will give.


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## Martin in Holland (13 Oct 2015)

I've got another graph....


 
Light is not always placed the same distance from the tank every time, you need to consider  this too.


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## robert2191 (13 Oct 2015)

Thanks not sure of the height of the tank , it should be delivered Thursday so will check then


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## alto (14 Oct 2015)

The above is a very simplified diagram, better understanding can be had by looking at this article which shows a three dimensional array of how light from T5 (& other sources) "falls" over the surface area of your tank 
Figure 2: Light distribution for the 36" ATI Powermodule 6X39W ATI Ecolux 6500K HO T5 Lamps

This article is also worth reading if you're interested in the complexities of lighting - often comparisons between lighting types or even different emitters of same type lighting are about as accurate as comparing apples & oranges   

Depending on tank dimensions, 2 HO T5 lamps may work very well, OTOH if your tank is 120cm x 60cm x 60cm, a single fixture with 2 T5 lamps will likely result in some areas being rather shaded compared to others.


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## Martin in Holland (14 Oct 2015)

The diagram is indeed very much simplified, but it's a start. It also doesn't include how long (big) the tubes are compared to the length of the tank.


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## ian_m (14 Oct 2015)

Martin in China said:


> It also doesn't include how long (big) the tubes are compared to the length of the tank.


This doesn't matter we are not concerned with length of tank. Generally longer the tank the longer the tubes you fit, so the lumens light per cm length stays approximately the same.


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## robert2191 (14 Oct 2015)

This was the light i was going to get http://www.allpondsolutions.co.uk/a...-t5-aquarium-four-tubes-thin-lighting-system/


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## robert2191 (15 Oct 2015)

Thanks for all the help got my tank and the measurements are 120(L) x 24(H) x 21(W)


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## alto (15 Oct 2015)

120cm long
24cm? high
21cm? wide


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## robert2191 (15 Oct 2015)

alto said:


> 120cm long
> 24cm? high
> 21cm? wide


Yes 


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## robert2191 (15 Oct 2015)

Haha sorry them last two inches 


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## alto (15 Oct 2015)

more sensible 
 ... anyway, look at the dimensions of the T5 fixtures, you may have
 2 x T5 in 18cm width
 OR
 4 x T5 in 24 cm width 

(I think, site is not loading for me now)

Depending on how you want to scape your tank, lights may be fine ... or less than ideal ... shaded areas of the tank are fine if they suit your goals.


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## robert2191 (16 Oct 2015)

alto said:


> more sensible
> ... anyway, look at the dimensions of the T5 fixtures, you may have
> 2 x T5 in 18cm width
> OR
> ...


 Think I might go with the 4 bulbs and if its to much then turn 2 bulbs off
Thank you


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## Martin in Holland (16 Oct 2015)

robert2191 said:


> Think I might go with the 4 bulbs and if its to much then turn 2 bulbs off
> Thank you



Better turn on 2 first, if it isn't enough turn on more, this prevents nasty unwanted algae growth because of to much light and not enough competition from plants as they still have to settle.


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## robert2191 (16 Oct 2015)

Martin in China said:


> Better turn on 2 first, if it isn't enough turn on more, this prevents nasty unwanted algae growth because of to much light and not enough competition from plants as they still have to settle.



Ok i will do it that way 
Thanks for your help


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