# 29g freshwater lighting question



## Technophil3 (Feb 24, 2014)

So i recently upgraded from a 20long to a 29 gallon. Shortly after i noticed my dual t5NO wasn't doing the trick so i added a single t8 50/50. My question is (still highly confused with the theories behind PAR) i want higher light on a budget. Looking at a dual t5ho 30" fixture. Would this be enough? Also contemplating on added the HO with my NO lights. Any thoughts? 

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## TropTrea (Jan 10, 2014)

Technophil3 said:


> So i recently upgraded from a 20long to a 29 gallon. Shortly after i noticed my dual t5NO wasn't doing the trick so i added a single t8 50/50. My question is (still highly confused with the theories behind PAR) i want higher light on a budget. Looking at a dual t5ho 30" fixture. Would this be enough? Also contemplating on added the HO with my NO lights. Any thoughts?
> 
> Sent from my LG-LS980 using Tapatalk


There is a lot of confusion between PAR, PUR, and Lumen.

When you measure PAR with a meter the perfect meter reads all light from 380nm to 700 nm which is the rang that photosynthesis occurs. However in reality there are two problems with most Par meters. The first is that they drop off in sensitivity on the extreme ends of the scale. Secondly is they value green light that has little photosynthetic value equal to the other waves.

Lumen on the other hand measures the light you see and is calibrated to the sensitivity of the eye. Since Green is the most sensitive to the eye the Lumen meters are tuned to give green light a higher value than red or blue light.

PUR is Photosynthesis Used Radiation and is the ideal. It is also the hardest to measure since various plants use some wavelengths of light more than others do. But if it can be measured it gives the most accurate reading for your plants.

Someone once wrote that if you took PAR and subtracted Lumens from it in the proper ration you would have a good idea on the PUR? I doubt it would be that simple.

The most important thing for plant growth is the lighting spectrum. Plants need both blue light which is under 500nm in length as well as red light that is longer than 620 nm. They also need this light in the proper balance.

With two HOT-5 bulbs on a 20 gallon tank regardless of the bulbs you were probably getting more than enough light regardless what bulbs you were using. However with the 29 gallon tank you are running 50% more water and 50% more space between the substrate and the surface. Therefore you either need to increase you wattage by 50% or make very good choices on your bulb selection. Using a bulb like a GE 6,500K bulb will increase the amount of blue light considerably over some bulbs that claim to have much higher Lumen. In the past I have great success combining the GE 6,500K bulb with there Chroma 5,000K bulbs that also have a good red and blue spectrum. But I would only change out one at a time and see how it improves your plants.


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## Bert H (Mar 2, 2004)

FWIW, I used to have a 29 gal and it was lit via a CF 55W and a standard 20W strip. It did a fine job. (Pressurized CO2 and dry fert dosed)


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## Technophil3 (Feb 24, 2014)

Bert H said:


> FWIW, I used to have a 29 gal and it was lit via a CF 55W and a standard 20W strip. It did a fine job. (Pressurized CO2 and dry fert dosed)


 I've thought about retrofitting an old hood to cfls

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## Technophil3 (Feb 24, 2014)

TropTrea said:


> There is a lot of confusion between PAR, PUR, and Lumen.
> 
> When you measure PAR with a meter the perfect meter reads all light from 380nm to 700 nm which is the rang that photosynthesis occurs. However in reality there are two problems with most Par meters. The first is that they drop off in sensitivity on the extreme ends of the scale. Secondly is they value green light that has little photosynthetic value equal to the other waves.
> 
> ...


I think i understand the basics of it all and as far as my current set up, I've got the 50/50 18w, a colormax 14w for my reds (came with the fixture), and a 14w 6700 (personally i enjoy 10k more for aesthetic reasons). 
I actually wasn't fully aware that you only needed a certain amount in the spectrum, that makes complete sense. My biggest issue is that i ran off and bought the first T5 dual strip i could find...not knowing that 24"L T5 bulbs are a pain to find around here.

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## TropTrea (Jan 10, 2014)

Technophil3 said:


> I think i understand the basics of it all and as far as my current set up, I've got the 50/50 18w, a colormax 14w for my reds (came with the fixture), and a 14w 6700 (personally i enjoy 10k more for aesthetic reasons).
> I actually wasn't fully aware that you only needed a certain amount in the spectrum, that makes complete sense. My biggest issue is that i ran off and bought the first T5 dual strip i could find...not knowing that 24"L T5 bulbs are a pain to find around here.
> 
> Sent from my LG-LS980 using Tapatalk


I'm running a combination of a 39 Watt ATI Aqua Blue Special and a 39 Watt ColorMax on my 40 breeder. The first few weeks were murder as the lagea went out of control untill the plants cought up with the rest of the tank. Now I'm harvesting hornworth out of the tank every other week and it is crystal clear. The big difference is I'm running HO T-5's and your running standard T-5's. Note the color MAX looks very dim compared to the other bulbs.

I just fired up my 120 with a pair of 54 Watt and I'm seeing the same thing running a combination of GE 6,500K and an ATI Purple Plus.

A word of caution with a 10,000K look is that you would have a tank with a lot of blue light and only a little red light. Not the greatest balance for plant growth.


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