PAR LEVELS theory w/o a PAR METER

[dnguyen1]

Hey guys,

I may try my hand at a single acropora frag and was reading that PAR levels should be between 350-500. I figured I better research a bit on PAR and learning about it before taking the dive.

Is PAR as linear as : the closer the piece is to the light the more intense the PAR levels will be and the lower or further out of the spread of the light the less it will be?

Thanks... so technically if a light lets say something like a POWER COMPACT, if the coral is like 1 inch away from it would it potentially get enough PAR? thanks!

 

[Tripod1404]

For a distant point light source (like sun), yes. For most aquarium lights, no.

In an aquarium, at equal depth, center of the tank gets more PAR compared to the corners. That is because the light source is not a single point. There is light coming from the top as well as the sides.

When something is in the middle, it gets light from all the sides with minimum possible travel time. When something is on the corner, only the light just above it has the minimum travel time. Light coming from the other side of the tank needs to travel trough the water before reaching to the target.

As a result, a lower central location can have a higher PAR compared to a higher location at a corner.

 

[dnguyen1]

For a distant point light source (like sun), yes. For most aquarium lights, no.

In an aquarium, at equal depth, center of the tank gets more PAR compared to the corners. That is because the light source is not a single point. There is light coming from the top as well as the sides.

When something is in the middle, it gets light from all the sides with minimum possible travel time. When something is on the corner, only the light just above it has the minimum travel time. Light coming from the other side of the tank needs to travel trough the water before reaching to the target.

As a result, a lower central location can have a higher PAR compared to a higher location at a corner.

That makes a lot of sense, so it's like a dome... ideally then, directly below and close to the source is what will generate the most... is this why T5 is such a viable option because it's equal spread?

 

[Tripod1404]

That makes a lot of sense, so it's like a dome... ideally then, directly below and close to the source is what will generate the most... is this why T5 is such a viable option because it's equal spread?

Kinda, T5 give better spread but still the center of the tank gets more light compared to the corners.

You can think about T5 bulbs like a very long fireplace. You would be warmest if you stay close to the center as heat will be radiating from all directions. But If you move to the left corner of the fireplace, you will only get warmth from the front and from the right. Now, lefter you move, less warmth will come from the right side and so, you will feel less warm even if you didn't move away from the fireplace but just moved left. Heat is infrared radiations so it behaves exactly like any other type of light.

 

[dnguyen1]

Got it, that makes a lot of sense, this is helpful.