Chagrin:
redtop03:
from what I've read about some LED drivers,I assumed that if you have a driver that ran at 1000ma you could connect 2 strings of 500ma LEDs and it would split the 1000ma current between the 2 strings....Exact opposite. Very difficult to balance current between two strings of LEDs in parallel; heat, age, etc. will throw off the balance and/or it will just be generally unstable.
You must be trying to run a massive heap of LEDs. You should try looking for an AC-powered driver, but going that route you won't be able to dim them (well, the cheap ones are typically not dimmable). Then again if you have that many LEDs you could turn them on and off in groups (relay board/shield, etc.) for the same effect.
I will need between 100 to 150 3w LEDs for a 360 gallon aquarium reef tank,I've found a few different drivers that will serve my needs and work with the Arduino but after seeing this shield,I thought it could simplify my build a great deal....
I'll look into the AC LEDs as well....I really want the dimming feature of the Arduino and the power efficiency of LEDs....currently,I use six 250w metal halide lights for illumination but there's never more than 2 at a time on,I have them connected to a controller that turns 'em on in a series to kinda mimic the sun moving across the tank but the tank looks odd partially lit 
thank you for the suggestions and help,I'm still learning about LEDs and still have a lot to learn,and I appreciate all the help I can get