Do I need to seal this concrete?

[randythawkins]

I will be using a large plastic stock tank as my settlement chamber. It will have one drain in the bottom center. I would like to slope the bottom, towards the drain, with concrete (similar to shower floors but with more slope) and plan to use concrete to do it. I know I would have to seal it if the concrete were used as a pond liner with the backside facing soil because I wouldn't want water to seep out but, since the concrete will be inside the the tub, do I need to seal it? I mean, so what if it soaks up water...concrete footings for fence and mailbox posts do it all the time. And there is nothing toxic to the fish in the concrete is there?

I don't think I need to but wanted to ask the community before I proceed.

Thanks,
Randy

 

[Mmathis]

Not related to your question of sealing, but just trying to picture this, and wondering if you would get debris trapped underneath the sloped concrete? And if so, would that ever be a problem?

Before I built my pond, I had a "watering hole" for my box turtles that was a deep flower pot saucer. The boxies were still pretty little then, so I used concrete around the perimeter edges inside the saucer to make a sloping surface so they could easily climb in and get out. There was always crud trapped underneath the concrete that had to be "power washed" out, as the usual rinse didn't get at it.

And that may not be an issue...

 

[randythawkins]

Not related to your question of sealing, but just trying to picture this, and wondering if you would get debris trapped underneath the sloped concrete? And if so, would that ever be a problem?

I planed on caulking around the edges where the concrete would meet the plastic (on the top outside perimeter of the concrete and the center where it meets at the drain). I figured that would keep the solid materials out even if water soaked through the concrete and eventually flooded the area between the bottom of the concrete and the tub.

Even if some debris did get in that narrow area I don't know that it would ever be a problem...only a limited amount could settle in the small gap and would it ever be comparatively more than what just does not get drained out of the pond? I dunno but, in my mind, seems like a negligible amount compared to the overall system.

 

[Mmathis]

I planed on caulking around the edges where the concrete would meet the plastic (on the top outside perimeter of the concrete and the center where it meets at the drain). I figured that would keep the solid materials out even if water soaked through the concrete and eventually flooded the area between the bottom of the concrete and the tub.

Even if some debris did get in that narrow area I don't know that it would ever be a problem...only a limited amount could settle in the small gap and would it ever be comparatively more than what just does not get drained out of the pond? I dunno but, in my mind, seems like a negligible amount compared to the overall system.

Hopefully, not a problem, and even so, I'll bet the swirling action would help there, sort of like a self-power-wash.

Have read both ways regarding sealing concrete/cement. And have read many pro's & con's. Some have issues with potential leaching, and some say it's not significant. But as far as the water soaking in and flooding the space between the container and the concrete, I don't think that it would happen that way. Just be sure to adequately cure the concrete.