Reduce powerhead speed?

[tailspot]

I have 2 Koralia Nano 240 powerheads in a 9 gal nano. The flow is nearly perfect, but I would love to reduce the power of one just a little. Clearly I know very little about electricity, which this question demonstrates, but since many lights can be dimmed, is there a similar way to safely reduce the power to a motor like this without damaging the unit?

 

[BLADEYAMAHA]

http://www.reefsanctuary.com/forums...ay-post-pics-photobucket-nanoreefing4fun.html

 

[BLADEYAMAHA]

I dunno.