Will bentonite harm fish in a pond?

No, bentonite will not harm fish in a pond. In fact, bentonite clay can actually be beneficial for fish and the health of a pond as it can assist in water purification which can increase dissolved oxygen content and remove heavy metals which may be beneficial for overall fish health in aquaculture. Bentonite clay is often used as a pond sealer because it has the ability to absorb and hold large amounts of water, which aids in maintaining consistent water levels. Additionally, its fine particles can help bind pollutants and heavy metals, acting as a natural water purifier beneficial for fish residing in the pond. However, It's always advisable to confirm specific concentrations used in your application of bentonite to assure safe use.