Stones in Koi pond keep falling

[poconojoe]

GB; mortar isn't waterproof. Trust me, helped rebuild more than a few chimneys with my dad (mason) once upon a time. Made cement aquariums that were waterproof, too. Cement ( Portland) is the better choice. And, I could make a very sticky mortar -- it's just a closer ratio of course sand to mortar that makes it that way. Plus, there's a reason they used to coat block basements with a cement coat and not mortar.

He probably didn't realize the stones were under water.
I thought the stones were around the perimeter edging outside of the pond, then I saw the picture.

 

[GBBUDD]

@poconojoe brings up a good point . The bio film will need to be removed from the rocks for the concrete to stick. To get mortar or waterfall foam to stick even using a pressure washer will be a bit of a challange. You do have a small pond i would guess.

Yes i understand the stones are in the water. I can read occasionally. Doesn't need to be water proof there's obviously a liner. The sides are just to tall and steep . They need to drain clean . Then add the mortar/ portland. But if they go that far might as well re dig the shelves . Angle the sides so the rocks hold or just pull out the baseballs and buy a skid or two of stackable rock. I used flatish rocks in dead pool but they are not stacked as much as they are laying on the angle similar to what they have here but i spray foamed them in place. Its only a year old and holding strong. My last video shows this area pretty well its toward the beginning of the video

 

[reefsr]

Just a thought: I would recommend removing the rocks. They will probably end up doing more harm then good, and are already causing you some frustration (enough to get on here and ask for help, anyway). They also give the fish a lot more swimming space due to the insane amount of rocks you have; removing them would give the fish a lot more space in the already small pond (for koi).

If you're dead set on rocks, GBBUDD had some pretty good ideas.

 

[Lisak1]

I'm a big proponent of any rock that is in or on the edge of a pond needs to be able to be stepped or walked on safely. The interior of the pond is no exception. If someone or something were to fall in, your stacked rocks would likely collapse if they were to try to climb out. You'd have a big mess and possibly even a dangerous situation.

I'd remove all the small rocks from inside the pond. It appears you have a shelf near the top - get some small boulders that are large enough so you can set them on the shelf where they are at least half covered by the water with some rock above the water line. That will help conceal your exposed liner and give you some spaces between them for marginal plants to break up the line of rocks. It's also more natural looking than a whole bunch of small rocks precariously stacked on the edge.

How is your waterfall held together?