I have digged a rather large pond (about 10x10 meter and 1.5 deep). I want to seal it but in a natural way. So no plastic or concrete. I was looking into Sodium bentonite (I was reading about that) but I only can get it with Polymer mixed in it. That doesn't sound natural to me. Any other suggestions? I am living in Thailand (in the north) and the soil is kind of an orange silt type of soil.

Kind regards,

Peter

Okay, there are two different types of bentonite, and I'm sorry, I'm not sure which is which, but one works better than the other. You will have to hope someone smarter than me responds.

Your pond is large enough, you should have a soil specialist come look at your site and make sure it is stable. I dug a much, much, much smaller hole to make a earth pond, six feet by three feet, by a foot and a half deep. That stupid pond threatened to take down my hillside.

Is there any tight stiff clay, the kind that is used to make bricks, available to you? You might find some in a river bank. If so, you could line the pond with about four inches of it and get a good seal.