Hello! I am brand new here and have a question about what size gravel to use for a bubbling rock/disappearing pond. We dug the hole, lined it with sand, added the liner, put in more sand, then filled it with #57 gravel. I just came from the "pond" store; they said I should have used #2 gravel, that I would lose water volume with #57 gravel. Well, okay -- but I already have a 5' x 10' x 18" hole now filled with #57 gravel.

So my question is this: Given the size hole we have, and given that we've already filled it with gravel ... should we LIVE with lower water volume, or should we shovel the gravel out and fill it with #2 gravel instead? We haven't put the actual 800-pound bubbling rock on yet; if we NEED to change the gravel, obviously we want to do it NOW before we have the rock delivered and installed.

Naturally, I'm hoping to hear that #57 gravel will work just fine ... but we don't want to have problems later down the road. Thanks!!!!

New2This -- Welcome to Pond Boss.

You've unfortunately stumbled into a deep can of worms, filled with quicksand. Plus, unfortunately, most of us here do not have a lot of experience with your type of pond. We mostly deal with earthen/clay sealed ponds, water table ponds filled to the water table, and privately owned lakes.

Please don't let this deter you. We'll be glad to answer any questions you might have.

I've been buying aggregate (river gravel, crushed gravel, stones, rocks, sand, etc.) for nearly 50 years. What a mess. There are some definitions. There are some standards, but . . . It is a murky world.

Here are two sites may help: Luck Stone Product Application Chart

Crushed Stone

Anyway, I'm not sure what the "pond store" people were suggesting. Water is displaced by volume. A cubic foot of rock is a cubic foot of rock. A cubic foot of rock will displace a cubic foot of water.

Not all rocks, stones, and crushed rock/stone are created equal. Some have minerals, or other substances that can be good for fish. Others can kill your fish. I usually suggest that you put a small amount of the aggregate in a cup of vinegar. Generally, if it foams, don't use it for fish.

Good luck,
Ken

I have no idea where you obtained the technical specs for constructing this feature, but they are entirely incorrect. The feature built as you described is guaranteed to fail. Your dimensions are fine, only a reservoir to allow for free flowing water to supply the pump is a must. Your set-up as described will rapidly clog with wind blown debris resulting in pump failure and a very labor and time intensive cleaning task. Matrix blocks, available under different brand names, are the usual choice to create the open, free flowing void under a surface layer of gravel along with a pump vault that will allow for ease of access for pump maintenance and for flushing the reservoir when required.

Catmandoo -- Thanks for the links! Our bubbling rock pond won't have any fish; it's mostly a "splash zone" for birds and butterflies.

Instar -- I should have said that the pump was inside of a "vault"; a large plastic box perforated with holes, so free-flowing water will seep through the gravel into the pump vault. And we plan to install the 800-pound rock in a location OTHER than directly on top of the pump vault in case we ever need to access the pump. I hope that makes a difference in your prediction of failure. :-(