HydroFarm 24" T5 lights and Footcandles
 

I am in the process of setting up my Exo Terra Orchidarium. The tank is 24"x18"x24". I considered an HID, but they output too much heat. According to HydroFarm their 24" T5 lights with 6400K bulb put out about 2,280 Lumens. What I would like to know is what would the Foot Candles be for a setup of six 24" T5's assuming that the reflectors are close to the top of the tank and the distance from the plants to the multi light source is about 18". There is suppose to be a formula for figuring this out, but I don't have a clue. I am looking to have about 2,500 foot candles or better. Will this work or do I need to consider multiple compact fluorescents?

I think it should work.
I use the longer 48 inch T5's, in an 8 bulb array. I can easily get 2500 foot candles at 18 inches. Indeed, I can get that at 24 inches!!
As I don't have the exact set up you are asking about, I can't really give you exact experienced numbers.
Sorry!

Hello :) how are you managing 6 lights? Are these single tube units? Double tube units? I don't think you'll need six to light a tank of that width, although I'm sure it is fine either way...you should definitely be getting enough light at 18"...and remember that the length of time you keep the lights on will effect the plants ie a plant like a catt listed to require 3000 FC will probably fry a little if given 3000 FC for 14-16 hours lol.

PS I know it's a bit controversial but I might suggest aiming for a 5000 kelvin bulb, or a mix of 6400 and 3000K bulbs

Thanks for the responses. The Hydrofarm T5's come as one bulb one reflector,but are designed to be linked together with a maximum of eight lights. I picked 6 bulbs to insure even coverage over the 24 by 18 inch area. I'm not worried about too much light because I can elevate the reflectors. The concern was if there would be enough. I plan on using 4 ea. 6400K lights and 2 ea. 3000K bulbs hopefully giving a more mixed spectrum.

I went straight half and half with my 2' T5's. I have 6 bulbs on 3 different ballasts that are going to be setup to turn on in order every 3 hours and then reverse that at night. I also have a moonlighting effect because this is really going to be a paludarium which i will eventually get some animals in. Its a 40 gallon breeder, and i think i went overkill with the lighting system, but i built it myself and am very happy with it. I am thinking on keeping 1 set of lights strictly for emergency lighting if needed. Who knows, but i dont have anything growing under them yet as im about to start building a stand for the tank. Im running the same lighting three 6400K and three 3000K. Also have gren and blue LED's for moonlighting, not sure what ones im going to go with, as green wont interupt photoperiod, and blue looks alot cooler than green, more scarry looking is what im going for, but then its photosynthesisable which can interupt its "night"??!