Building A Pocket Pond with Concrete- Sealant Needed?

Hey permies,

My partner and I are building a pocket pond within a food forest landscape to catch and store water (partially from the High Tunnel that’s up slope from it) that we can use, provide habitat for aquatic life and plants and be a cool landscape feature. We live in the Ozarks (zone 6b) and made the pond quite deep- 4 ft at its deepest with sloping sides.


It’s our first time building a pond and we’re finishing up the concrete work now (ratio 1.5 sand to 1 cement) and wondering if we need to seal it.

I am not so concerned with the slow seep porosity of concrete, but more curious about the leaching of lime from the concrete into the water making it more alkaline (is this true) and also the lifetime of the concrete- will it last longer if we seal it?

Have you built a pond and used concrete? Did you use a sealant? Thanks for your help!

That's about the same size as my little pond.  It started out with a tarp,  but the rodents ate it. So I concreted it, but it cracked. I sealed the cracks, but it seeps. I am happy the rodents can't get through it, but next step is I will build it taller and put in used carpet and billboard as a liner. That's because I want it to hold lots of fish and not just be a puddle.

It sounds like you are using a mortar mix, not concrete.
Concrete contains sand, aggregate and cement.
Mortar is sand and Cement.
There will be no leaching of lime, because none appears to be being used.
Unless the material cracks, it may be self sealing from the point of view of leakage.

Any sealing agent may not be healthy for your useses described.