The AC adapter on my light crapped out so I bought one with selectable DC output voltage. The original one was 12 volts but I noticed that the lights get considerably brighter at 16 and really bright at 19 volts. I like the look at 16 volts so I'm going to keep it there. LEDs might burn out sooner but we'll see if the lights can take it. I might look into building a circuit where I can dial a specific voltage to create a dimmer.
Be careful. As you increase the voltage the junction temperature of the diode also increases. Too much and the LED's will burn out. You can increase your heat removal with heat sinking and/or fans to help wick away this heat to make the diodes last longer.
I took my BeamsWork light apart and noticed that the entire aluminum outer housing is being used as one big heat sink for the LED circuit board. So it's a good thing that the housing is a bit warm. I decided to not drill holes in it because of this. I have my air conditioning set to 74, so I think/hope the diodes will survive the extra "juice". I'm curious how my plants/algae will react to the increased light.