I am trying to figure out the light intensity within an inch of the surface of a t8 bulb. I know it is over 100 umols but need to know if it is over 200 umols which would photoinhibit the algae I am growing. 200 is optimum but anything over is really bad news. Anyone?
I don't know the answer, but I do know that that PAR value would apply only in a very small region right next to the bulb. A few inches farther away and the PAR drops considerably. You would have a very shallow water level in the tray you would be using as an aquarium if the substrate will be an inch from the bulb.
FWIW, I just pulled a reading off of a 2x overdriven t8 and it was around 400 at one inch. Like Hoppy said, it falls off real quick even a wee bit further from the bulb. Should be dropping at 1/distance.
Thank you both. My substrate is about an inch and a quarter from the bulb under about a half inch of water. How does the output of the overdriven t8 compare to my ballast factor 1 f32 bulb? If it is double then 1 inch gives me my 200umols. If not I think I can extrapolate close enough if I CAN FIGURe OUT the 1/distance formula you mentioned???? but let me know if you come up with anything else. PS growing algae is fun. mine gets covered in a solid mass of o2 bubbles in about 2 hours and stays like that until I knock it down. It looks like caldo but should give over to spiro hair type algae soon...