TerraPond is a clay additive for ponds. There are others, Ultimate Koy Clay, being one of the first and better clays. The dosage will cloud the water for a short period of time, but in no way makes it a mud pond. These clays are calcium bentonite clays and due to the fine size, they tend to flocculate fines making them easier to remove. Some of the sales information would lead you to believe that they will add necessary minerals to the pond, which they may if the pond is really devoid of them, but generally, not so much. Some will add the clay to the food so the koi will consume it. May be good, many primitive peoples will eat clay to remove toxins from their bodies and potentially gain some minerals in the process. I do use the Ultimate periodically as a polish for my pond.
Zone 7 A/B
Keep your words sweet. You never know when you may have to eat them.
Richard