I have scraped out my pond twice in the last 25yrs.The reason I scraped out the pond was because of build up of sludge on the bottom.As you know this sludge can cause algie,weed and clarity problems.I need to do it again but it is such a large job,also the mess and loss of fish.My question;does adding bactria to the pond really work,it sure would be a easer way.thanks...jimmy