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notsuperwoman

Bonding Stones to the Bottom of a Pond

notsuperwoman
11 years ago

I have a poorly designed concrete "pond" that is more like a 6-inch deep, flat bottomed reflecting pool, with about 30 s.f. of surface area. It is ugly just with the clear pond sealer, so i put large river rock on the bottom. The stones make weekly muckvac very hard.

I would like to set the stones permanently on the bottom so we could really brush on and around the rock for a thorough cleaning, rather than remove, move and get under the rock, which has never gotten the thing clean.

I've tried getting advice from a tile/masonry forum, to no avail. And, in my research, I have come across black foams, hydraulic cements, regular mortar, plastic cements. My eyes are now crossing. Basically, I would like some advice on a good product to trowel across the bottom and push the stones into, so they stick out of the cementious "bed" and look like rocks, but stay in place during cleaning. It would have to be a product that stands up in a submerged environment.

In terms of toxicity, the hope would be to have at least some pond plants in submersed baskets, but fish probably need a little more depth than I have.

Thank you in advance for any thoughts.

Comments (8)

  • groundbeef
    11 years ago

    Personally I think it's a bad idea to try to permanantly fuse them to the bottem. At 30 square foot, you are looking at approximatly 5x6?

    I'd leave them be unsecured. You can move things around, and really get in there and clean if needed. Once you glue stuff down, it just makes it harder.

    Just my $.02.

    If you must secure them, black foam would probably be best. It's for underwater environments and should last. I'd be leary of any type of caulking.

  • notsuperwoman
    Original Author
    11 years ago

    Hi. Gr. Beef. Thanks for your reply. It's actually an L shape, 2x12 feet on one leg, and about 5x8 on the bottom leg, but with a 4x6 foot concrete paver smack dab in the middle of that part. So it's like a little maze to clean. The only realistic way of cleaning it well is to remove all the rocks and replace the water (while feeding my plant some nice sludge!) The rocks are heavy. I know, it's a mess! And no drain or rain protection to boot, so I can't leave it a dry rock bed. ! I think I have a future in designing mosquito safe havens, should that need ever arise.

  • notsuperwoman
    Original Author
    11 years ago

    Beautiful!

    Have you noticed much shrinkage around the rocks? Mine are 2-3" in diameter so that might be an issue.

  • waterbug_guy
    11 years ago

    I did not see any cracking at all. I assume there's been some subsurface, but can't tell. You do want to lay the mortar and push the rocks into the mortar so there's mortar under the rock too. I don't think 2-3" would be a problem, I think there would be less visible cracking with smaller rock.

    This is time consuming. You might consider using the methods they use to produce exposed aggregate. Even stamped concrete. 30 sq ft isn't too bad. But for me I used larger and larger rocks the more I did, using large flag stone eventually. Depends on the look you want.

    I did use small 3" river rock in some areas to vary the look. It didn't turn out that well for me, kind of just looked like concrete. Unless you you're going to use chlorine to remove all algae the small rocks get a little hidden.

    Thought about using broken slate? Cleans really well and you can get a modern look if algae is controlled. Pretty inexpensive too, faster to lay.

  • djdee4
    8 years ago

    waterbug_guy, do you need anything underneath the mortar and rocks to prevent leaking?

  • waterbug_guy
    8 years ago

    Liner beneath is required. Mortared rock is not water tight.


  • Debbie Downer
    8 years ago

    Thank you! Ive been wanting to do this around the shallower shelf edges of my pond - the deeper sections I'll leave black liner (which gets coated nice and green). What I worry about is lime leaching in and how it would affect water quality. Here in Wis. the alkalinity and hardness of water is almost off the charts - cannot afford to add in any more. Does the concrete reach a point where its old or hardened enough that its not going to do that, and if so how long does that take? Of is it going to be a continuous problem?


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