# Optimal PAR for CO2 vs low tech tanks?



## Daximus (Oct 19, 2011)

It has a lot to do with the depth of your tank and your reflectors. I don't know much about light, but Hoppy is a rocket scientist...see link below, might help you. 




http://www.plantedtank.net/forums/lighting/105774-par-vs-distance-t5-t12-pc.html


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## VeeSe (Apr 16, 2011)

You don't need higher than low light for a CO2 injected tank if you don't want to. 40-50 micromols of PAR should be fine.


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## DKRST (Jan 20, 2011)

VeeSe said:


> You don't need higher than low light for a CO2 injected tank if you don't want to. 40-50 micromols of PAR should be fine.


I thought 50 micromoles was medium light? What are the PAR ranges for "Low and medium" lighting?


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## VeeSe (Apr 16, 2011)

It's all relative. You shouldn't really worry about "labeling" things with strict cutoffs. Everybody has a different cutoff and there's really no need for strict definitions.


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## DKRST (Jan 20, 2011)

Can't help it, I'm a scientist - I like precision, but I do realize it's not an exact thing...


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## jcgd (Feb 18, 2004)

DKRST said:


> I thought 50 micromoles was medium light? What are the PAR ranges for "Low and medium" lighting?





VeeSe said:


> It's all relative. You shouldn't really worry about "labeling" things with strict cutoffs. Everybody has a different cutoff and there's really no need for strict definitions.


+1



DKRST said:


> Can't help it, I'm a scientist - I like precision, but I do realize it's not an exact thing...


If you like precision, around 50umol of par has been found to roughly be the threshold for being about to grow any plant. Anything less and you start to limit the species you can grow.

Add co2 to any setup and increases the amount of light the plants are able to use. I don't know the real numbers, but with good co2 a tank with 20umol of par will grow plants like it has 30umol of par, even though it doesn't. Literally, it is fuel for plants, like drinking Gatorade if you are running a lot. Run a marathon without water and electrolytes and you'll pass out. Give plants too much light without co2 and they stunt. Same with fertz.


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## jcgd (Feb 18, 2004)

DKRST said:


> I thought 50 micromoles was medium light? What are the PAR ranges for "Low and medium" lighting?


The high tech/ low tech label is really dumb, imo. But people have a need to label things, so there it is.

It's more like 50umol is sufficient light... for everything. In a absolute world, 50umol is enough light. Any thing under is 'under lighted' and anything over is 'over lighted'. Both are okay if you want to a) limit the species you can grow, or b) enjoy trimming, wasting power, etc.


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## DKRST (Jan 20, 2011)

jcgd said:


> The high tech/ low tech label is really dumb, imo. But people have a need to label things, so there it is.
> 
> It's more like 50umol is sufficient light... for everything. In a absolute world, 50umol is enough light. Any thing under is 'under lighted' and anything over is 'over lighted'. Both are okay if you want to a) limit the species you can grow, or b) enjoy trimming, wasting power, etc.



That's what I needed! I don't really don't want to do the upper bleeding edge "High" light, but I was wanting to know what's a good PAR, with pressurized CO2, to grow the majority of non super-finicky plants and get decent color.

Thanks!


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## Hoppy (Dec 24, 2005)

DKRST said:


> That's what I needed! I don't really don't want to do the upper bleeding edge "High" light, but I was wanting to know what's a good PAR, with pressurized CO2, to grow the majority of non super-finicky plants and get decent color.
> 
> Thanks!


Getting decent color may depend mostly on what plants you are referring to. Alternanthera reineckii will have decent color with low light, but some plants only get really red with higher light. And, other plants get more red if you restrict their nitrate supply (as I recall), because they are struggling to be healthy.

I find that around 30-40 mms of PAR may be a good range for little or no CO2 addition, but 40-50 may give you some algae problems without CO2. At least that was what I saw with my last tank, which is no longer set up. And, remember, things like filter pipes up near the water surface see a much higher PAR than stuff at the substrate level, so some BBA may start up on those high in the tank things, while lower in the tank, there is no BBA. But, once the BBA gets going good, if it is left alone, it can then spread to lower areas in the tank. So, good tank maintenance is also needed even with low light. For lazy people like me this is at times challenging.


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## DKRST (Jan 20, 2011)

Hoppy said:


> ..... And, remember, things like filter pipes up near the water surface see a much higher PAR than stuff at the substrate level, so some BBA may start up on those high in the tank things, while lower in the tank, there is no BBA. But, once the BBA gets going good, if it is left alone, it can then spread to lower areas in the tank. So, good tank maintenance is also needed even with low light. For lazy people like me this is at times challenging.


Thanks for the advice Hoppy and jcgd! That's the guidance I was looking for, general PAR ranges to start from - with and without CO2. I'll tweak it up or down from there. I had that exact BBA issue on some driftwood that reaches almost to the top of my tank. Of course, I think it was most likely due to a PAR of 200+ at the surface drool from running 2x T5HO tubes before I knew anything about lighting! I scrubbed the BBA with a toothbrush and used Excel on the spots. Seemed to take care of the issue. Obviously, I'm only using one bulb now and have suspended the fixture above the tank!


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