I was told I should put lime in my pond. How can I find out how much lime to put in my pond, how to apply it, and what kind of lime I should use?

A soil test, preferably done through your local Cooperative Extension office, will tell you how much lime, if any, your pond requires. A method frequently used with good results is to apply the amount of lime recommended by a soil test, then apply one-fourth of that amount each succeeding year to keep lime requirements satisfied. A liming treatment may last almost indefinitely in ponds with no outflow, but most ponds have at least some water discharge or are drained and refilled periodically. Most ponds with acid soils and moderate water outflow will probably need lime every three to five years.
Agricultural limestone (calcium carbonate or dolomite), hydrated lime (calcium hydroxide), and quick lime (calcium hydroxide) are the most common liming materials for ponds. Agricultural limestone is not harmful to humans and will not cause high pH in water like the other forms of lime. It is the best and safest liming material to use in farm ponds. New ponds can be limed before they are filled. Spread the liming material evenly over the dry pond bottom. A disk harrow can be used to mix the lime into the soil. In ponds already filled with water, limestone should be applied evenly across the water surface. In small ponds, this may be done by spreading bagged limestone from a boat. In larger ponds, where several tons may be required, a platform can be built on the front of a large boat or between two boats tied together. Bulk limestone can be loaded (do not overload!) on the platform and distributed across the pond surface with a shovel. Even distribution across the entire bottom is essential for good results. Do not apply limestone while a pond is being fertilized. Limestone settles phosphorus out of the water, making it unavailable. Apply lime during late fall and winter. This will give it a chance to react with the acidic bottom mud before the spring application of fertilizer.