The aeration/bacteria method will only *at the most* reduce the muck build up a few inches per year.

When thinking about dredging, consider how many gallons of water the pump moves and how fast you would dewater the pond during the dredging process if you didn't use dewatering filter bags.

You might want to look into those.

www.hoosierpondpros.com

[Linked Image from lh6.ggpht.com]
http://www.pondboss.com/subscribe.asp?c=4
3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).