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PAR in freshwater vs salt


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If everything else is the same:   same lighting, same sensor placement, same depth in the water, same temps...    Would a PAR reading in fresh water be different than salt water?

I'm thinking it would have an impact, due to difference in density in the two liquids, and that salt would have more of a PAR loss at depths than fresh.

Do PAR meters have switches/toggles for this?

I'm curious because I wonder if tests could be run in fresh water, for simplicity and cost savings, and if fresh water based test data would be meaningful to salt water applications.


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PAR meters don't have settings for fresh or salt, they're just measuring available light at the sensor.  I'd guess, strictly speaking, saltwater would absorb slightly more light than freshwater but I'm pretty sure we're trying to split hairs.  PAR meters aren't that sensitive (lux meters are roughly 50 - 55X more sensitive) and I wouldn't think a PAR meter would show a difference.

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Thanks Tim.

My thought is that I'll have the 180 resealed and a stand built in about two weeks.  I don't want to do a leak test with salt.   Expensive leak test.   I'll do it with hose water. 

I'd like to do a PAR test with a few lights at that depth, during the leak check, to see what I want to do.   I have ideas.    Some are more expensive than others.   :D

Also, want an eyeball check on what kind of coverage the lights get, spread, and visuals too.

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