We sell  Bio-Clean Microbial Pond Clarifier but I have never tried them.  So I did alittle research on them and thought I'd share the information.

They contain beneficial microbes (bacteria and mold cultures), which eliminate excess problem-causing nutrients from your pond.  They also contain microbes, which provide the comprehensive removal of bottom sludge.  The microbes will not only degrade cellulose (one of the primary components of plants wastes), but will also eliminate pectin (fibrous materials also found in plants), xylanase (found in various parts of plants also), and most importantly lignin (the heartiest component in leaves and stems of plants).

Bio-Clean microbial pond clarifiers include two very specific cultures for removing excess, problem-causing ammonia, urea, nitrites and nitrates from the pond water.   Bio-Clean contains microbes for achieving odor control, by eliminating the dead and decaying organic wastes causing the odors.

Water Clarity - Bio-Clean also utilizes microbes to achieve water clarity.  Water clarity is accomplished when the microbes eliminate the dead and decaying organic wastes, which float in the water as suspended solids.  As these organic wastes are removed, water clarity drastically increases (from virtually no clarity, up to 6+ foot depth of clarity after only a few treatments.

Usage:  One 3 oz Bio-Clean tablet per 2500-3000 gallons of water or 20 per surface acre of water per month.  You apply around the edges of the pond.  You can purchase it here.