^ Not true... its the bulbs that are rated 10,000K and up that are NOT suitable for freshwater tanks, 6700K - 8000K is normally considered optimal for plant growth, and then 10,000K for better light penetration... but anything over 10K and up, you have to be very careful, as anything at or over this K rating will most likely cause a lot of algae growth...
So i would say maybe swap out the bulbs for something not quite as strong, since as you said, its only fish in the tank, so you may want to find the best lighting that will help make your fish stand out more...