How to reduce the depth of my pond

[parabous]

I have a 2 metre deep pond that is an old concrete water tank, I want to reduce the depth to be more manageable and so that I see the Koi. What depth should I go to and what should I use to reduce the depth?

Concrete? Stones? Sand?

 

[hamstermann]

I have a 2 metre deep pond that is an old concrete water tank, I want to reduce the depth to be more manageable and so that I see the Koi. What depth should I go to and what should I use to reduce the depth?

Concrete? Stones? Sand?

I'd suggest milk crates covered by cobble, then gravel. That way you still have the water volume to help with balancing the pond - larger water volumes are more stable chemically and with temperature than smaller ones. The rocks would also help with having more surface area for beneficial bacteria to grow on.

As far as depth, that's tougher to answer. What's your climate like, what fish will you be putting in, if any, and how many? Will you want shelves for plants?

 

[Mmathis]

Does your pond have a liner, or is it just the concrete? And is the concrete sealed in any way? Also, what are the overall dimensions of the pond/well: length and width?

I know, so many questions and no answers, but it’s info that will help us give you the best choices.

 

[j.w]

How wide is it?

 

[jimbo]

I'd suggest milk crates covered by cobble, then gravel. That way you still have the water volume to help with balancing the pond - larger water volumes are more stable chemically and with temperature than smaller ones. The rocks would also help with having more surface area for beneficial bacteria to grow on.

As far as depth, that's tougher to answer. What's your climate like, what fish will you be putting in, if any, and how many? Will you want shelves for plants?

My pond depth is 4 1/2 feet. Every time I get in with my waders on and bend over slightly, I wish my depth was 4 feet! I think I would be concerned about milk crates, and filling up the area with rock. The sludge that will build up in that overtime would be significant and difficult to remove. Alternative choice might be to take your fish out and put them in a holding tank, Fill in the base of your pond and put in a new liner at the depth you want. Just a thought.

 

[hamstermann]

My pond depth is 4 1/2 feet. Every time I get in with my waders on and bend over slightly, I wish my depth was 4 feet! I think I would be concerned about milk crates, and filling up the area with rock. The sludge that will build up in that overtime would be significant and difficult to remove. Alternative choice might be to take your fish out and put them in a holding tank, Fill in the base of your pond and put in a new liner at the depth you want. Just a thought.

yeah, you'd need a cleanout with the milkcrates and rock. Think of it like a bog under your pond instead of to the side of it.

 

[parabous]

The pond is about 8 metres in diameter (nearly circular). I will be keeping koi and my climate is tropical, lows of about 5C and highs of about 38C, averaging 28C in summer and 5C in winter at night.

It's concrete and must be sealed because it is an old water tank.

I've just been recommending stacking these Aquablox things to 1 metre in height so that I can keep the water volume and have the effective depth reduced to 1 metre, of course there are no straight edges so it will leave gaps all round for the fish to hide away (is my thinking).

AquaBlox® Water Storage Modules

Aquascape AquaBlox® Water Storage Module displaces water for Pondless Waterfall and rainwater collection projects.

www.aquascapeinc.com

 

[Mmathis]

Is there any way you would consider adding a liner! You could backfill with sand/dirt, compact it, then install the liner. That’s what I would do (I think you would have to drill holes through the concrete for drainage, but not an expert in anything).

Do you plan on walking around on the pond bottom? You want something sturdy.

One thing to consider is that in extreme cold / extreme heat situations, depth can be your friend. Your temps (I had to convert them — crazy American, here) don’t sound too bad, in fact, a lot like mine here in the Southern US, but my summers are hotter. You were asking about depth. Koi like and need a lot of space, so don’t go too shallow.

Sorry I can’t be more helpful.

 

[j.w]

I might think concrete might be a good choice as you are going to seal all the other concrete there anyways. Wonder what @GBBUDD thinks? I think he works w/concrete a lot don't you @GBBUDD ?

 

[hamstermann]

I've just been recommending stacking these Aquablox things to 1 metre in height so that I can keep the water volume and have the effective depth reduced to 1 metre, of course there are no straight edges so it will leave gaps all round for the fish to hide away (is my thinking).

AquaBlox® Water Storage Modules

Aquascape AquaBlox® Water Storage Module displaces water for Pondless Waterfall and rainwater collection projects.

www.aquascapeinc.com

Those are just overengineered expensive milk crates. you can buy them and put them in but regular milk crates would be sufficient.

Is there any way you would consider adding a liner! You could backfill with sand/dirt, compact it, then install the liner. That’s what I would do

That's a much easier idea.

 

[GBBUDD]

There is a pond th

Those are just overengineered expensive milk crates. you can buy them and put them in but regular milk crates would be sufficient

There is a huge difference from a milk crat to an aquablock as generic term. You won't find an engineer that would use milk crates as a water storage that is underground and is going to Carry a Live load. Aquablocks and or matrix block are designed for this.
Milk crates are made for carrying and yes stacking. But here is the difference. Matrix blocks have all the sides. Atop and bottom locked together. Granted only by plastic pins but it does the job.
Each block has two center dividing walls as well so there are 8 sections to 5 on a milk crate but again they are locked in place to each other. The milk crates sit in a notch on the side and are not designed to come anywhere near the tolerances needed to burry tons of stone on then and to then drive on it to boot.

The aquablocks have another advantage being they are easy to cut and I use zip ties to resecure them together.
They do have a substantial cost to them but are also the most structuraly sound that can also be cut.

Don't get me wrong milk crates are perfect for other projects just don't get caught using stoles crates.
And no not all concrete needs to be sealed concrete at 5000 psi and above generaly are more water proof.
But there are many coatings today like plaster a very well known material and liquid rubber or even some paints

 

[parabous]

Well, the work has begun, I've pulled the plants and dropped the water level, grid comes out in the next two days.

Once the grid is out, then comes decision time on the depth and design. Being two metres deep makes putting a fountain and in fact any plants or anything in the pond a challenge. Perhaps I will need to drain it in order to put something in the middle that the fountain can sit on.

Dilemma: Do I catch the fish, drain the pond and start again or something else...? I feel like I have little choice.

I put some water into those two holding tanks for the fish, should I go that path, if not, I have them for rearing babies later.

 

[parabous]

I forgot to post some before shots, some before the weeds took over too.

 

[hamstermann]

Interesting. I've never seen a water tank like that before. What's the grid made of? It looks maybe pipes with a net stretched over them?

 

[parabous]

Yes, it's steel fencing with galvanised fence mesh. I think it's been in there for 35 years.