If those two measure exactly the same, then you should definitely try running both LEDs in parallel on the same driver. Especially since you have everything terminal blocked. See what you think. That will still be a heck of a lot of light for that tank.
As for shunt resistors:
I don't know what your math was...
You have a
current source. that will supply 900mA thru whatever load it's driving. The resistor's duty is to pass 200mA if you want to reduce the current that would otherwise pass thru the LEDs.
8.95V / 0.200A = 44.75 ohms
This resistor dropping 200mA will dissipate:
0.200A x 0.200A x 44.75 ohms = 1.79Watts. Make sure this resistor is rated at 5watts or more of power dissipation.
Caveats. Since this shunt resistor will cause less current to flow thru the LED the operating point will be different which means the voltage will be different which would change the resistor value a little. The result is you will need to adjust the resistor a little from the computed value above.
Use a resistor like this:
http://www.digikey.com/product-detail/en/AVT25-50-10%/AVT25-50-ND/257624
Set it to about 44 ohms then measure its resistance. Install it across the emitter. Power up. Measure the voltage across the resistor and using ohms law compute the current thru it. If you don't like the result POWER OFF and then re-adjust then power back on. Step and repeat. NOT following this procedure may likely blow your emitters.