Thanks, I'd probably still scale it up. I forgot to say, the tank is 125 gallons and I'm not convinced that 6 leds can power enough growth to get rid of all the nitrate.
And if the light requirement really was that small, the savings from using LED over CFL isn't worth the effort.
So anyway you'd recommend more purple/blue than red?
Also, doesn't parallel LEDs risk runaway failure?
No purple blue AND red... More red the better.
Parallel strings are much less a problem w/ constant current drivers..
I have, as an example 1 string of 1W LED's w/ 5 in series and 3 parallel strings.
Due to a bad soldering job (I orig. thought I could save money by ordering heat sink stars and raw diodes separately..ended up not being worth the hassle).. Lost 2 diodes on different branches.. lone string didn't fry... Don't ask me how that works though.. but it seems to. If your really worried there are balancing circuits or even simple fuse on each branch that are an easy fix for this..
also you can mitigate the problem by choosing a driver and parallel string count as to under drive the LED's (best anyways since LED's get less efficient as to reach max current)
slightly. W/ enough parallel strings even losing one will only increase the current on the remaining enough to just boost, not fry them..
Say you have a 1.2A driver and are running 4 parallel strings at roughly 300mA per string (w/ 350mA LEDS w/ tolerance up to 500mA)
Losing an entire string will only cause 1.2A into 3 causing them to go from 300mA to 400mA.. not enough to pop them..
also you need to watch the Vf of the individual colors since they can vary enough to be mildly problematic.. Best to match Vf to a driver. though not necessary if you know what you are doing, it makes things simpler...
Reds tend to have a much lower Vf than other LED's ..
Emitting Colour: Red
Color Wave Length: 650-660nm
Reverse Voltage: 5.0 V
DC Forward Voltage: Typical: 2.2V Max: 2.4V
DC Forward Current: 750mA
3W blue high power led lamp 440nm~460nm for the aquarium light,3.0-3.6V
sticking w/ R/B for a minute (add purple later.. You would possibly do 12-660nM red and 4 440nM blue.
(4x3.3=13.2V @ 750mA, you could use a 12V driver @700-1000mA all LED's in series)
(12x 2.2= 26.4V @ 700mA driver all in series.. no need for any parallel strings but 2 drivers..)
Add Violet to the blue string
Emitting Colour: Ultra Violet
Color Wave Length: 420-425nm
Reverse Voltage: 5.0 V
DC Forward Voltage: Typical: 3.6V Max: 3.8V
DC Forward Current: 700
Adding 4 to the blue string will only push your V to 24V approx (I'd do 3 for a total of 7 @700mA driver )..
any errors/omissions here others are free to correct..
57W of targeted LED's should be plenty..