Square pin [::] or straight pin [....] bulbs? Each type has a bulb that the other doesn't.
In the square pin you can get an 8800K bulb, which is a crisp white—but not blindingly so. This is my personal favorite bulb.
In the straight pin there's the GE AquaRay 9325K bulb—a somewhat acquired taste due to its pink/purple hue—but the plants love it and it can really make irredescent fish sparkle.
Then there are 6500/6700K (can be somewhat yellow/green in hue) and 10000K (may washout colors in shallower tanks) bulbs available for both.
Any of these will do. In the end it comes down to personal preference from an asthetic standpoint.
In the square pin you can get an 8800K bulb, which is a crisp white—but not blindingly so. This is my personal favorite bulb.
In the straight pin there's the GE AquaRay 9325K bulb—a somewhat acquired taste due to its pink/purple hue—but the plants love it and it can really make irredescent fish sparkle.
Then there are 6500/6700K (can be somewhat yellow/green in hue) and 10000K (may washout colors in shallower tanks) bulbs available for both.
Any of these will do. In the end it comes down to personal preference from an asthetic standpoint.