# Photosynthetic Potential



## bioniccruiser (Nov 14, 2011)

someone can correct me if I'm wrong- it doesn't work that way for light. it's not like extra ferts in the water that having more plants would use up. more light is more light hitting each plant. the only help more plants would be is if some that could use the higher light level shaded ones that would be getting too much light.


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## Daximus (Oct 19, 2011)

I think _bioniccruiser_ is all over this. 

Light isn't something measured by volume, it's measured by intensity. The volume isn't really quantifiable. You don't say how many pounds of light do I need for this tank. :hihi:



> In conclusion, a plant can reach its 'photosynthetic potential', in which any additional light added to the aquarium, will not promote any further photosynthesis.


I'm obviously not Tom Barr, but I suspect what he was getting at is that there is a certain point where more light isn't going to do anything good for your plants. They are limited by other factors (Co2 and available nutrients), and ultimately by their ability to photosynthesize. Meaning, even if you had everything absolutely perfect, a plant can only do so much photosynthesizing on one day, or given period of time.


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## plantbrain (Dec 15, 2003)

You might get more growth, but keeping up wit that growth, and dealing with algae and adding CO2 might be tough.

Theory is fine......but practical matters.....eg keepign up with things.........is another matter, algae starts becoming more an issue the higher you go with lighting.

The old analogy: 

You drive pretty safe at 25 mph(lower light), if you wreck, no big deal.
You can see and respond to problems pretty reasonably.
You get pretty good gas mileage(efficient growth) 

If you drive say at 100 mph, if you wreck, things tend to be pretty bad.
You need to be much more responsive to issues.
You do not get the same mileage and efficiency.

Many are skilled enough to be fast drivers.
Most are not.

While your car might do 100 mph, few of us ever drive that fast.


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## samamorgan (Dec 31, 2011)

I drive a motorcycle daily and am sorry to say i probably go over 100mph at least once a month. It's kinda stupid how easy it is to do. Yes, i'm perfectly aware i wont survive a crash at 100mph, but it probably wouldnt be much different at normal freeway speeds either. Hell i don't even really try to hit that speed, i just pull on the gas, happen to look down and im 30mph over the speed limit 

That is a great analogy though, and i was amazed how quickly things went wrong in my 70 PAR tank when the Co2 reg crapped out.


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## mindfestival (Jul 23, 2011)

Awesome +1. 

So rather than folks focusing on all this 'high light' jazz, how _low_ can i have my lights?

I know that the wpg rule doesnt really apply, especially for t5's. 

Regardless, say i was at 1wpg, over a 100 gallon heavily planted tank, in theory given that the only limiting factor was light, would i still have a lush aquascape, albiet slow growing?

Thoughts appriciated one again.


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## Daximus (Oct 19, 2011)

mindfestival said:


> Awesome +1.
> 
> So rather than folks focusing on all this 'high light' jazz, how _low_ can i have my lights?
> 
> ...


That's kind of what I do. I have a dirt tank, that I dose moderately, with Co2, and I run really really low light. Again, the watts per gallon is silly, but for reference I'm running 1.42 w/p/g....of T8 lighting. 

You do need half way decent reflectors in my opinion to help the light get down to the floor of larger tanks though.


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## plantbrain (Dec 15, 2003)

mindfestival said:


> Awesome +1.
> 
> So rather than folks focusing on all this 'high light' jazz, how _low_ can i have my lights?


This is a wiser better question.



> I know that the wpg rule doesnt really apply, especially for t5's.
> 
> Regardless, say i was at 1wpg, over a 100 gallon heavily planted tank, in theory given that the only limiting factor was light, would i still have a lush aquascape, albiet slow growing?
> 
> Thoughts appriciated one again.


Yes, the 180 Gal tank I have is an example that is well managed by using the lower end of lighting.

Even the 120 Gal, it has high light, but only for a few hours.

You have 2 main factors, intensity and duration.
I suppose spread/evenness are also large players......

This assumes CO2/nutrient independence.

But......you can slow growth down with high light and good CO2, by limiting ferts......but you waste the light energy(Excess/waste etc) in doing so.

If you run a high light tank, then run it full out! Good ferts, CO2 and high light.

My 120 Gal is an example that.

The 60 Cubes I did a little while back are on the other spectrum with CO2 and low light.

The lower the light, the easier CO2 and dosing is. 
So if you want to avoid water changes, dosing etc, and have an easier time with CO2/algae......then that is a wise method.

In all cases, I can see little argument against rich sediment like say ADA aqua soil. Aesthetics etc for say Black Flourite sand might be one case......but few other argurments.


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## mindfestival (Jul 23, 2011)

plantbrain said:


> Yes, the 180 Gal tank I have is an example that is well managed by using the lower end of lighting..


May i see a pic of this?

I have had a look at a number of your tanks, and have tried to work out how low, or high, your lighting is but fail to find descriptions. 

For example this tank


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## Hoppy (Dec 24, 2005)

Notice that that tank has the light suspended above the top of the tank. Since light intensity drops with distance from the light, clearly the same watts per gallon with the light sitting on top of the tank and with it a foot above the top of the tank give you far different light intensities. So, watts per gallon is not a measure of light intensity. PAR, in micromols per square meter per second, is the measure of light intensity as it affects plants.


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## samamorgan (Dec 31, 2011)

mindfestival said:


> May i see a pic of this?
> 
> I have had a look at a number of your tanks, and have tried to work out how low, or high, your lighting is but fail to find descriptions.
> 
> For example this tank


God i wish i could get DHG to grow that well, that's so beautiful.


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## mindfestival (Jul 23, 2011)

Eleocharis Acicularis i believe?

I am trying to get this to carpet myself.

Plantbrain - how was this planted initially?

I have just spaced mine about 3 inches apart, all over the substrate.

I hope this will spread with routine trimming...


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