Lux meter with submersible probe

[Steve Maxwell]

Hello....
Anybody have any recommendations for a good lux meter with a submersible probe? I'd love to get an Apogee Par meter, but don't want to spend the $$$. Also, any good way to convert Lux to Par or Lux levels for various coral types?

Thanks!

 

[saltyfilmfolks]

milwalkee $75 easy google search
lux meter waterproof

I want to spend the $$$ but cant

https://www.reef2reef.com/threads/lux-meter-how-is-it-useful.246962/#post-2899884

https://www.reef2reef.com/threads/adjusting-leds-with-a-meter.246540/#post-2897064

 

[Steve Maxwell]

milwalkee $75 easy google search
lux meter waterproof

I want to spend the $$$ but cant

https://www.reef2reef.com/threads/lux-meter-how-is-it-useful.246962/#post-2899884

https://www.reef2reef.com/threads/adjusting-leds-with-a-meter.246540/#post-2897064

Great! Thanks! I realize it is a easy google search, but was wanting to see if anybody on the site has any experience with them or specific recommendations.

 

[mcarroll]

Anybody have any recommendations for a good lux meter with a submersible probe?

I'm not aware of any other submersible lux meters.

If you make it $56 I think that Milwaukee is a no-brainer....and these guys apparently have it on sale:
http://www.testequipmentdepot.com/products.htm?item=MW700&ref=gbase&gclid=CMr065WYvMwCFVE0aQodi2cFWA
(@saltyfilmfolks found this later....just reposting)

I'm not positive, but it may ONLY take readings under water. If so (check the manual), I'd still get a cheapie $15 handheld lux meter for measuring out of water. (A cheap handheld is all I use.)

Also, any good way to convert Lux to Par or Lux levels for various coral types?

The easy, shorthand way I use is based on these rough equivalencies:

2000 PAR = 100,000 lux = Direct Sunlight At Sea Level​

That gives you an easy conversion factor of 50.

I.e.:

2,000 x 50 = 100,000
100,000 ÷ 50 = 2,000​

That has worked well for me in almost any scenario.

Note: If you haven't read the Dana Riddle articles (only one or two I think) where he talked about lux meters and PAR meters, conversion factors, etc.....you should. :) The one nugget I'll pass on is that every lighting system will actually have its own conversion factor. Interesting!

However, as I said, I've found that a generic conversion factor (based on sunlight) is still accurate enough for us in this case.

If it helps, remember that most corals, in general, are not particular at all about lighting levels:

• Anything from 5,000 lux up to 100,000 lux will keep corals alive.
• 20,000-80,000 lux seems to be the "safe range" - meaning that growth is good at the low end but light stress isn't causing major problems on the high end.
• Around 30,000-50,000 lux seems to be a sweet spot. Maybe it's coincidence, but this seems to be the range where most manufacturered LED fixtures max out.

But that's all in general.

Once we're talking about a particular coral, especially once it matures, there are practical considerations. For example, while frags seems almost supernaturally adaptable and resilient, mature corals do not generally respond well to dramatic lighting changes.

If you're setting up a new tank with fresh frags, you may have quite a bit of latitude in deciding what intensity to run your lights. I have a tank I set up that runs at about 14,000 lux. Grows the same stony corals as the main display that gets around 50,000 lux...probably a bit slower is all. I started it with (mostly) fresh frags from the main display.

However, if you're upgrading lights, or moving corals to a system with different lights, you really want to forget about your choice....instead, the idea would be to match the old tank's intensity as closely as you can. You can try to match the color too, but you should set color how you like it in my opinion. As long as you pick some color combo that's at least vaguely "reef-like", it'll work and the numbers will be fine. We're not being precise enough for that to matter, nor is there a need to be. :)

A cheapie lux meter will get the job done in both scenarios. :)

 

[Steve Maxwell]

I'm not positive, but it may ONLY take readings under water. If so (check the manual), I'd still get a cheapie $15 handheld lux meter for measuring out of water. (A cheap handheld is all I use.)

So, if you use a handheld lux meter out of water, how do you measure light at different levels within the tank? If you point it at a specific area of the tank through the glass does it give an accurate reading?

 

[mcarroll]

You can really tell everything you really need to know from surface measurements.

Measuring below the water is interesting and probably useful in some scenarios, but not necessary for this. It's good to remember that these are very rough measurements, no matter how we take them and no matter which tool. (You have to spend into the four or five digits to get a really good light meter, and even then it's not straight forward to accurately measure LED's or aquarium lights - it takes some doing.) It's also good to remember that corals aren't so exacting/are pretty adaptable. Your "Crazy Marketing Name" Chalice does not require exactly 130 PAR, for example. There's certainly an acceptable range, but it's just that - a range. Anything around 130 is likely to be fine.

I haven't gotten around to finding/reading them yet, but I've read about studies where wild corals were moved to different depths - some more shallow, some deeper - to observe their reactions. Mortality was common....but it might be interesting to know if they defined any of the acceptable ranges. The amount of change a coral can be expected to tolerate, in other words.

Anyway, if you want to know the light level in a certain area of the tank, it's easy to watch the shadow cast by the sensor as you move around taking samples over the water....you're (mostly) measuring the light that hits that shadow. (You'll note that the shadow isn't completely black, so there is other light hitting that spot too....but it's relatively very faint. That's why it still looks like a shadow. :D My guess is that, within the scope of that shadow, you're measureing 80-90% of the light hitting that spot. Good enough!!)

I don't know if I addressed any or all of your concerns, but that's enough typing for now. Let me know! :) :) :)

 

[Steve Maxwell]

Sounds great...Might actually download one of the free lux meters for my Android and see how that works. I've just started buying corals other than zoas & 'shrooms, so I'm a little paranoid ;)

 

[saltyfilmfolks]

if your zoas are growing dont sweat it.
There's a lot of overthinking. It a very good and important IMO parameter to test and know where its at.
BUT.....
And get the $15 handheld, esp w led.