Deepening an existing pond

[Art]

I have a small pond and it was built some 15 years ago. It has a mixture of goldfish and koi in it that were all purchased when it was built. The fish have now become large but unfortunately I can't make a bigger pond due to lack of space so I wondered about extending the depth by building a higher wall around it.
The liner is a heavy butyl rubber version that is held in place by a wall at one end and slabs around the other three sides.
Obviously a new liner is needed but do I lay one over the existing one? Join Butyl to the existing one to extend it or what would you suggest?
I don't want to spend a fortune in doing it and I haven't got anywhere to move the fish to while its done. The good thing is that my existing filter box and pump will easily cope with a larger volume of water.

 

[MitchM]

Welcome Art.
You'll need a new liner, but I don't know how you can do it without removing the fish.
You can just lay a new liner over the existing one, and you'll need to be watchful of ammonia buildup once the fish are in the pond with the new liner.

 

[Mmathis]

Hello and welcome!

What size (dimensions and gallons) is your current pond. And by how much are you wanting to deepen it?

One thing that stands out for me is that when you make the pond bigger by adding depth, you aren’t increasing the surface area and that’s where gas exchange takes place. Maybe that’s only a factor if you change the dimensions by a certain formula (unknown to me, but maybe @MitchM would know).

 

[EricV]

Typically you'd lay a new one over the old one and make sure the old one doesn't hold water (trap water between the liners) by cutting some holes in it.

In the US we have intex inflatable pools which are amazingly cheap and good places to store fish while doing serious maintenance. Maybe you can find a used pool like that?

 

[sissy]

warning lay something over the top because the fish may jump out .I used window screen o my stock tank and a pump with a small filter and a aerator .Do not feed the fish and try using as much of the pond water as possible and have a water test kit handy .The fish get stressed out really fast

 

[GBBUDD]

If you want to save money and do more work if the old rubber isn't to old you could always splice the rubbers together

 

[TRose]

I have a small pond and it was built some 15 years ago. It has a mixture of goldfish and koi in it that were all purchased when it was built. The fish have now become large but unfortunately I can't make a bigger pond due to lack of space so I wondered about extending the depth by building a higher wall around it.
The liner is a heavy butyl rubber version that is held in place by a wall at one end and slabs around the other three sides.
Obviously a new liner is needed but do I lay one over the existing one? Join Butyl to the existing one to extend it or what would you suggest?
I don't want to spend a fortune in doing it and I haven't got anywhere to move the fish to while its done. The good thing is that my existing filter box and pump will easily cope with a larger volume of water.View attachment 112146

How large (gallons) is your existing pond? What size pump (gph) do you have? How many fish is in your pond?

 

[GBBUDD]

@TRose these posts are from 2018

 

[brokensword]

@TRose these posts are from 2018

sheesh; either GB is learnin' or @Mmathis , you're a bit tardy on this one!!!

 

[Mmathis]

sheesh; either GB is learnin' or @Mmathis , you're a bit tardy on this one!!!

GB beat me to it!

 

[GBBUDD]

sheesh; either GB is learnin' or @Mmathis , you're a bit tardy on this one!!!

Gb remembers the post.............. question asked............ never returned

 

[Art]

How large (gallons) is your existing pond? What size pump (gph) do you have? How many fish is in your pond?

Hi the pond is 6x8feet and holds approximately 500 gallons. The pump is a 5500 lph and the filter can cope with 5000 gallons.
I went ott on the pump and filtration as I have appx 70 fish

 

[brokensword]

Hi the pond is 6x8feet and holds approximately 500 gallons. The pump is a 5500 lph and the filter can cope with 5000 gallons.
I went ott on the pump and filtration as I have appx 70 fish

I hope you don't really have 70 fish (goldfish?) in only 500 gallons; that's a sure fire way to have issues. Before koi, I had over 100 gf in 2500 gallons and thought it was a bit crowded.

 

[Art]

I hope you don't really have 70 fish (goldfish?) in only 500 gallons; that's a sure fire way to have issues. Before koi, I had over 100 gf in 2500 gallons and thought it was a bit crowded.

Well at one point there were ver 100.
None are diseased and most years I may lose 1 fish due to old age.
The goldfish and the koi breed most years and I just simply let them be.

 

[mrsclem]

@Art - how long have you had your pond? How did you go from over 100 to 70? How many koi? We get so many new members that say my pond and fish have been fine for years and now suddenly my fish are dying. The one thing that changes is the size of the fish. Larger fish- more waste= fish problems. Sounds like you are handling it with great filtration.