What is the ideal amount of light for a new 70L tank?

jaypeecee

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The often spurious claims of manufacturers ;)
Hi Tim,

Couldn't agree more. But, it's worse than that. Some manufacturers treat their customers with disrespect. The more specialized the product, the more they pull the wool over the eyes of their customers. In so doing, they ignore the fact that some customers design the type of product that they are selling. Of course, it's not just aquatics. The story's the same across other business areas.

JPC
 

Wookii

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Just to extend on my initial question, with a couple of follow up questions if I may:

1. If I set my lighting for a sunrise/fade in and sunset/fade out, how does that affect the chosen photo period? For example, say I have a 1 hour period for each, should that 2 hr period be considered a 1 hour contribution to the total photo period (given the average 50% of selected max light)? Or does in not work in a linear way like that?

2. In the absence of being able to measure the physical par values, if I raise the light 300mm above the tank (rather than its default position of resting on the tank rim) how does that affect the level I should initially set the lighting to? For example if I follow Tim's recommendation above of an initial 6 hour photo period at 50% light intensity, does that recommendation change if the light is higher, or not?
 

Edvet

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1) remember algae can profit from lower light values then your (other) plants, much lower. So i wouldn't start using sunrise/sunsets till all is growing very healthy. So 2 hours added are 2 hours added for the algae.
2) Raising will lower lightvalues squared to distance, double the total distance will give 1/4 of the light.https://petapixel.com/2016/06/02/primer-inverse-square-law-light/. Less light longer time can work in low tech tanks for instance ( so lower light, no CO2 needed), within reason. Low tech tanks can work in 12 hour light even, just not in high light ( unless you are prepared to use large amounts of stable CO2 levels)
 

Wookii

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1) remember algae can profit from lower light values then your (other) plants, much lower. So i wouldn't start using sunrise/sunsets till all is growing very healthy. So 2 hours added are 2 hours added for the algae.
2) Raising will lower lightvalues squared to distance, double the total distance will give 1/4 of the light.https://petapixel.com/2016/06/02/primer-inverse-square-law-light/. Less light longer time can work in low tech tanks for instance ( so lower light, no CO2 needed), within reason. Low tech tanks can work in 12 hour light even, just not in high light ( unless you are prepared to use large amounts of stable CO2 levels)
Thanks for the reply Edvet - good point on the lower light levels, I hadn’t thought of that. I’ll save the sunrise and sunset for a couple of months then.

On the light levels vs distance, thanks for the link - I should have known that really given time I’ve spent setting up projectors in the past!

If I use reflectors to limit the light spill/beam to the surface area of the tank, the same area as if the light was at the tanks surface, presumably that narrowing of the beam of light reduces the losses to less than 75% per doubling of distance? (Though I appreciate there will still be losses as they won’t be ‘perfect’ reflectors)
 

Edvet

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Well the inverse square law will still work, just with reflectors you increase the original output, just like LED's with a directional output give higher light to start with.
 

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