Apogee MQ-200
Hi,
I am pretty sure as far as the waterproofing goes, silicon aquarium goop should work.
I am an Apogee MQ-200 quantum meter user.
Leveling and orienting to true north (or true south in the southern hemisphere) is an issue with the angle of the sun throughout the day in locations (mounted sensor) where information is being logged throughout a season or year. :gw
Consistency in sensor orientation is an issue for repeatability, building and using a jig, part sensor mount, part story stick, part angle mount without affecting the reading.
Using the jig, then reliably moving the sensor so that readings can be taken vertically to gain accurate point measurements at various levels to get repeatable measurement is trickier then it might seem.

(Not unlike this sentence.

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I find it easier to get proper readings in ponds and lakes then aquariums.
Then correcting for the particular sensor is important. Knowing what part of the spectrum is over or underestimated.
The LI-COR meters are more accurate and auto correcting and so forth, but are also much more expensive.
Biollante