Skriz;1064684 wrote: You're talking about the iwasaki 6500k lamp. Phenomenal par, but needs supplementation to even out the colour and clean water; any tannins will only boost the yellow appearance.
Ushio bulbs are great quality. Their 10kk is a par monster. The 14kk comes next and is a crisp white. The 20kk after that. Made in Germany, so you get a consistent lamp.
Radium 20kk is another great lamp. Again, made in Germany, so the quality is there.
If all you're looking for is massive growth, the iwasaki or Ushio 10kk are great options. As for colour, that all depends on your taste.