Concrete lined pond advice

[BarbAZCA]

I've seen lots of posts about this topic. So many random thoughts/advice, I'd like to start again with my specific situation. I am having a small pond (with a waterfall) done by an 'expert' on ponds; never sure if they know everything. The situation: I am having the pond deepened with vertical sides to deter raccoons without having to cover it every night. The thought is to remove the fish to a holding tank (summer vs winter issues?), remove all the rocks & rubber liner, make the sides vertical to a finished depth of 3'. Then replace the rubber liner in the new pond up under the lowest tier of waterfall rocks. Add tinted concrete all around (rock lined pond has been a pain to clean), top with existing boulders integrated witha thick flagstone ledge set in concrete. The filter/pump box on the left side of photo will be kept as is to maintain current water level. Raise the bottom rocks of waterfall so raccoons can't swipe down to get fish. I have one year old goldfish and their babies, don't plan on koi or any other type of 'exotic' fish. Next up will be recommendations on plants to reduce algae and other maintenance. I wanted to put in a bog at the top, but the raccoons will trash it. What are the issues with tinted concrete? Any special concrete that will reduce curing time and leaching? Any other advice/thoughts?

 

[Lisak1]

I don't know anything about concrete, so I'll leave that to people with more experience than me. You live in a warm climate so you won't have the issues we do here in the midwest with heaving and cracking. I do have one question though - if you are hiring someone who claims to have experience, and you are able to verify they know what they're doing - ask to see their work, get references, etc - would you trust them for advice on using concrete in a garden pond? If not, I might just keep looking. I never like being the one telling my hired "experts" how to do the job I hired them to do.

A couple of comments - and I won't try to de-rail your thread, but for anyone reading in the future I wanted to point out a couple of things from your photo. You have trouble with raccoons - your pond is shallow but it's also basically a wade in and feast buffet because of your edge treatment. Too many places for the critters to stand in shallow water and fish from IN the pond, let alone from the side.

Also - you mentioned your rock bottom pond is a pain to clean. That's again a function of how your pond was built - it's basically a rock lined bowl, versus a pond with sides and a bottom. If your pond bottom was covered with a shallow layer of gravel and the bigger rocks were only on the sides, cleaning wouldn't be an issue.

I know you understand and you are addressing these issues in your re-build so your pond will function much better in the future. I just don't want someone to land on "rock bottom ponds are a pain to clean" without understanding how and why that can be an issue.

And now let's conjure up some experts to answer your question about concrete: @GBBUDD @combatwombat you guys have any suggestions? Or know anyone here who might?

Good luck @BarbAZCA ! Your pond is already a joy to you I can tell or you'd be filling the hole and calling it quits. You will be so happy when you have a pond that is easy to maintain and hard for the critters to disturb!

 

[BarbAZCA]

I don't know anything about concrete, so I'll leave that to people with more experience than me. You live in a warm climate so you won't have the issues we do here in the midwest with heaving and cracking. I do have one question though - if you are hiring someone who claims to have experience, and you are able to verify they know what they're doing - ask to see their work, get references, etc - would you trust them for advice on using concrete in a garden pond? If not, I might just keep looking. I never like being the one telling my hired "experts" how to do the job I hired them to do.

A couple of comments - and I won't try to de-rail your thread, but for anyone reading in the future I wanted to point out a couple of things from your photo. You have trouble with raccoons - your pond is shallow but it's also basically a wade in and feast buffet because of your edge treatment. Too many places for the critters to stand in shallow water and fish from IN the pond, let alone from the side.

Also - you mentioned your rock bottom pond is a pain to clean. That's again a function of how your pond was built - it's basically a rock lined bowl, versus a pond with sides and a bottom. If your pond bottom was covered with a shallow layer of gravel and the bigger rocks were only on the sides, cleaning wouldn't be an issue.

I know you understand and you are addressing these issues in your re-build so your pond will function much better in the future. I just don't want someone to land on "rock bottom ponds are a pain to clean" without understanding how and why that can be an issue.

And now let's conjure up some experts to answer your question about concrete: @GBBUDD @combatwombat you guys have any suggestions? Or know anyone here who might?

Good luck @BarbAZCA ! Your pond is already a joy to you I can tell or you'd be filling the hole and calling it quits. You will be so happy when you have a pond that is easy to maintain and hard for the critters to disturb!

When I first had the pond/waterfall built, it was basically a water feature with no thought to adding fish (which I did about five years later). Yes, I enjoy it a lot.

I find it amazing that people and the weather zone maps call my climate 'mild'. We get nights in the teens/20s during the winter and occasional snow that usually melts quickly. Interesting to me is that two previous batches of goldfish (that became raccoon meals) wintered over under pavers at the bottom - I didn't even know I still had fish. This batch of goldfish (they were feeder fish in the summer of 2021 and managed to have babies that I noticed the beginning of that winter) have been out most days for both winters.

Thank you for addressing the rock vs. concrete lining. I've consulted with two pond 'experts'. As you say, one said they don't recommend cement, they recommend rock, better for the pond's ecosystem. They would stack the sides with rock and cap it with larger rocks and thick flagstone set in cement that will supposedly hold the rock sides in place. My concern about this is if/when I drain the pond, step in to remove fish to a holding tank, and start cleaning (some power washing and removing sludge in to buckets), the rock sides will collapse. Do you have a pond built this way? What are your thoughts on this?

The other 'expert' says they only do concrete lined ponds, not rock. My concern addressed to him was about the curing process. He assured me that concrete never completely cures, but would be fish friendly in less than a month. I saw a post that said using 100% Portland Cement resolves the curing issue - not sure why.

Thank you for your reply and reaching out to two other pond forum users.

 

[GBBUDD]

In Arizona the first issue you'll have is not the winter temps but the summer and the uv rays. Heat and uv are the enemies of EPDM.

What you have there is a wadding stream easy for the racons to do their worst. We have tons of racoons here in the north east and I have seen Tracks all over pulling up moss and smaller rocks. Racoons will fish your pond if there is no other food available. Having no shallow areas for them to stand up on and yes i'm talking on two legs as they will lean up against the sides while they try to fish . They are very smart critters.
The other option to lessen their fishing is to have the water down from the edges of the pond. A foot would make it hard for them to fish but herons need closer to two to three feet.

Where concretes strength id epdm weakness . and epdms strength is concretes weakness. Concrete will not flex, cracks and delaminates in time and is hard to puncture. While epdm bends and flexes and won't crack until it has failed some years down the road.
If both are PROPERLY built the concrete is less of a worry but will cost about 1/3 or more over the epdm. The concrete today can have all kinds of additives to make it thinner and stronger. Fiberglass and other polymers can increase concretes strength and durability. A well rounded contractor in your area will know the mixtures that work best. As far as never curing well that's not exactly true. Even concrete fully exposed or placed under water will cure, it just takes much longer. The longer concrete takes to dry/CURE the better it is.
I would never do any concrete work like your planning without rebar and lots of it.

You don't need to take goldfish in, they will over winter down there just fine providing you add a pond breather or airstone. if you shut down your pump . That's definitely a personal preference
if your going with gold fish you can do either a bald liner or one with rocks while the rocks add naturalizing they also add additional surface area for bacteria and micro organisms a place to grow
You need to decide if your doing a de

 

[BarbAZCA]

In Arizona the first issue you'll have is not the winter temps but the summer and the uv rays. Heat and uv are the enemies of EPDM.

What you have there is a wadding stream easy for the racons to do their worst. We have tons of racoons here in the north east and I have seen Tracks all over pulling up moss and smaller rocks. Racoons will fish your pond if there is no other food available. Having no shallow areas for them to stand up on and yes i'm talking on two legs as they will lean up against the sides while they try to fish . They are very smart critters.
The other option to lessen their fishing is to have the water down from the edges of the pond. A foot would make it hard for them to fish but herons need closer to two to three feet.

Where concretes strength id epdm weakness . and epdms strength is concretes weakness. Concrete will not flex, cracks and delaminates in time and is hard to puncture. While epdm bends and flexes and won't crack until it has failed some years down the road.
If both are PROPERLY built the concrete is less of a worry but will cost about 1/3 or more over the epdm. The concrete today can have all kinds of additives to make it thinner and stronger. Fiberglass and other polymers can increase concretes strength and durability. A well rounded contractor in your area will know the mixtures that work best. As far as never curing well that's not exactly true. Even concrete fully exposed or placed under water will cure, it just takes much longer. The longer concrete takes to dry/CURE the better it is.
I would never do any concrete work like your planning without rebar and lots of it.

You don't need to take goldfish in, they will over winter down there just fine providing you add a pond breather or airstone. if you shut down your pump . That's definitely a personal preference
if your going with gold fish you can do either a bald liner or one with rocks while the rocks add naturalizing they also add additional surface area for bacteria and micro organisms a place to grow
You need to decide if your doing a de

Thank you for information on the options. I wanted to do a bog on top of the waterfall but the raccoons are in there all the time and tore through all plants I've put up there and in the wading pool. I'm hoping that once the pond is deeper I can grow plants directly in the pond without raccoons getting to them. I leave the pump and waterfall on all year with the goldfish in the pond and haven't had any problems. In 11 years of running the pond (it was shut down for 7 years because my housesitter didn't want to deal with it) I'm on my second pump. Love the photos in your showcase - very nice.

 

[GBBUDD]

the racoons are more than likely hunting for frogs in your bog. if you plant creeping jenny and the likes the racoons can rip them up all they want they grow quick.

Plants aren't a must have but they do help tremendously

 

[Laaf]

I had a similar situation. My too shallow pond had to be covered with fencing to protect my fish from raccoons. And when I was trying to get someone with experience to build a bigger pond for me, the concrete only ponds landscaping company had the best offer for me and built their first bog for me.

I disagree that raccoons will trash a bog. They never bothered my small bog. My big bog is too new to know yet.

A lot of the filtering and bacteria of the bog are in the rocks. So even if a raccoon digs around or eats/uproots plants, it is the easiest filter known for your pond.

 

[Lisak1]

@BarbAZCA - my pond is completely rocked. When a pond wall is properly stacked, you can climb all over it and nothing moves. Anything else would be either annoying or downright dangerous. We did this project as a DIY build, and have not had a single rock move in 13 years. If amateurs can do it, professionals surely can. Your walls need to be slightly sloped backwards, but not a lot. And you start with bigger rocks at the bottom course, which then gives the next row a firm, secure foundation. Each rock needs to be "locked" in place. It sounds difficult, but it's really just a learning process. the first thing you learn is to quickly move on from any rock that doesn't "fit" - if it doesn't easily "lock" in, choose another rock.) I climb in and out of our pond all the time with no issues. We built a spot in the wall that's essentially stairs for just this purpose. I get in to groom plants, move lights (or put them back where they belong when my fish decide THEY should move them!) shuffle around in the gravel, move the aerator, etc. (I don't recommend power washing a pond, but that's another conversation.)

To us in the midwest, "nights in the teens/20s with occasional snow" sounds like it's time to light up the barbecue! We get long stretches of nights AND days far below zero, snow that is often several FEET deep and lasts for weeks. The long periods of freezing (and occasional warming) wreak havoc on concrete because of the heaving that the freeze/thaw cycle creates. We manage it with driveways, sidewalks, porches, etc., but don't really put that kind of construction into a pond when you can use a liner that can handle the freezing and thawing with no problems. And our fish stay in the pond year round.

One last comment - I know you worry about the raccoons and the bog, but I think you would find that an established bog will be impossible for even the most wily raccoon to destroy. It takes a shovel and a pickaxe for me to remove grown irises from my bog - no raccoon is going to go to that kind of effort. @GBBUDD is right - they're just hunting the frogs that live in the bog. The trick will be getting them to leave the plants alone until they get well established and then I think you'll dissuade them from even trying.

 

[addy1]

I disagree that raccoons will trash a bog. They never bothered my small bog. My big bog is too new to know yet.

Our raccoons never bother the bog. The deer, different story, right now walk in it every night snacking on bog plants that are still growing.

 

[combatwombat]

I'm absolutely no expert on concrete, so take these thoughts with a grain of salt and ask your professional builders:

I don't like the idea of doing concrete over epdm. Doesn't make sense to me. The concrete can be the waterproofing layer (or, rather, the polymer placed over it), so if I were building a concrete pond, I would go that route for a much longer lasting and more easily repairable feature.

Using a 100% portland cement mix sounds like a bad idea. Cement isn't strong. It needs sand aggregate to bond to get its strength. I don't know how long a portland-cement-only mix would last, but I fear it would not be long.

I echo @GBBUDD re: rebar. Wouldn't build without it.

If I were going that route, I think I'd go gunite. More in the realm of pool builders than pond builders, but this is also the domain of high-end koi pond builders, so you may find some expertise in your area to tap.

The folks at koiphen love concrete ponds. You can likely find a lot of discussion about build details over there.

Ask lots of questions from any builder you get a bid from. Ask them about routine and long term maintenance and any build details they do to improve those things. Then feel free to bring those questions here and we can help you figure out if their answers are sound or full of it.