No, it's a count of photons as reported by an Ocean Optics spectrometer. Older OO software offered a conversion of counts to PFD, not sure if the new OceanView does that. I loved their early iterations, they were so easy to use. OceanView is unnecessarily complicated.
I'm guessing - skeletons of living corals can contain quite a few types of bacteria. Purple and green sulfur bacteria are photosynthetic and can absorb wavelengths around 850nm or so. This could be what the fluorometer saw. Or perhaps not. I spoke with a bioengineer in Texas about this and he was stumped. I'm not very concerned since I don't plan to illuminate the tank with only IR. On another note, European researchers have found that IR treatments can kill certain types of bacteria although details (to me) are sketchy.
A little background: There are two Photosystems - Photosystem I (PSI) and Photosystem II (PSII). Within each of these is a Reaction Center (specialized chlorophyll a) where the photosynthetic processes begin (or begins to get serious). The Reaction Center in PSII absorbs light at 680nm; PSI at 700nm. The problem is that there aren't many Reaction Centers, so photopigments called accessory pigments collect light and channel it to the Reaction Centers. These include chlorophyll a, chlorophyll c2, and peridinin. These collect light across a wide bandwidth, ranging from UV-A to far red (a little above 700nm.) Hence, red light isn't necessary but can be used if available.
