When you add two bulbs you don't double the Kelvin Rating, the wattage yes you can but not the Kelvin since that is only the measure of the color temperature. It's like trying to combine red paint with red paint, it will still be red paint but it doesn't become any brighter or duller.
Anything under 5,000K will be low lighting but there is more to classifying lighting than just your bulb. It also deals with how far the light is from the substrate, how well it's reflected into the light and then also the color temperature and a tiny amount of the wattage. But with your tank it would be considered very low light.
I run 10,000K LED's on my Betta tanks and it's not that bright for them, I do provide lots of shade for them if they chose to hide though. But my tank would be considered med-high lighting since the light is only 12 inches from the substrate and then the kelvin rating of the actual lights.
EDIT: I can go further into explaining PAR if you'd like, if the above explanation is enough just let me know ^_^
Anything under 5,000K will be low lighting but there is more to classifying lighting than just your bulb. It also deals with how far the light is from the substrate, how well it's reflected into the light and then also the color temperature and a tiny amount of the wattage. But with your tank it would be considered very low light.
I run 10,000K LED's on my Betta tanks and it's not that bright for them, I do provide lots of shade for them if they chose to hide though. But my tank would be considered med-high lighting since the light is only 12 inches from the substrate and then the kelvin rating of the actual lights.
EDIT: I can go further into explaining PAR if you'd like, if the above explanation is enough just let me know ^_^
Each tank is a 10 gallon, and the lights are about 13 inches away from the substrate. Substrate is basic pool sand so it helps to reflect some of the light and make things brighter.
