Simple submerge a water pump and aim it at the water's surface. The water will break the surface without causing undesirable visual disruption. To prevent the pump from clogging, you can use a pump sock . A must see site, Nice folks with an educational purpose. I just spent the hour drooling over Sweetwater blowers, hydroponic gardening stuff, tanks, and tubs that would make a fish nut crazy.
Prices are good on alot of stuff.
You'll thank me for the suggestion. Click the image to order your copy direct from them. SnoTabby shows just how far a Goldfish hobby can go. I will someday get around to going through and verifying all links. Introduction to the video.