i just went out to home depot today and bought a double fixture for a 36inch tank. I purchased a 5000K bulb and a 6500K bulb. I used to have a single 18000 K power glo bulb on there but have no success with keeping plants. It says the bulb is good for plants but after reading articles here, i think it is way to high(kelvin) for any plants. Do you think that 6500s or 5000s are better for plants?