Heated pond questions plz help

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AC Members
Original poster
Aug 3, 2016
Hey guys,

I am thinking of building a large pond with dimensions (6x1.5x2m) which will be 18000 litres and wondering what fish I could put in it I would rather have some cool exotic species than just normal goldfish and koi.

It will be a heated tank that will live in a large greenhouse in the garden to help with heat control.

Also would it not be too expensive to build it out of concrete and add a glass panel to the front

Thx guys


AC Members
Aug 13, 2009
There are lots of large fish that would be suitable. But the first thing you should do before adding any tropical species is figure out what temperature you can maintain year round economically.


Registered Member
Jan 28, 2017
You're talking about a pond of over 4000 gallons. Depending upon your location, heating the entire pond to a temp that will sustain tropical fish may not be feasible. Is your greenhouse heated year round? I have a 6,500 gallon pond in the central U.S. It isn't in a greenhouse, but it is protected from the worst elements by its location. We use a stock tank heater to keep an open area for gasses to escape during winter, but the rest of the pond freezes to a depth of several inches; thick enough for me to walk on with no trouble. Keeping a large pond at 78 F could require a very large heater.
Concrete and glass are not expensive materials, if you can make it work without leaks. However, concrete, when fresh, can leach harmful chemicals into the water. If you did decide to build with concrete, I would advise several full water changes and several months of seasoning before you added fish.
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AC Members
Apr 27, 2010
So Cal
a key question is "where do you live?" as mentioned above, your location and the ambient temperature you can keep around the pond will determine whether you are able to keep the water warm enough for whatever fish you want (as low as say 50F / 10C for hardy fish to 78F / 25C for tropicals -- possibly higher for some african cichlids).

if you want a window (which would be cool), at least part of the pond is going to be above grade. this increases the structural requirements a little. not so much to hold the water up as to prevent leaks.

concrete is a workable material and suitable, except it is hard to seal properly until it has cured and the ground has settled.

for a completely underground pond, a rubber liner (EPDM, do not use any of the others) is a lot easier and more reliable.

for an above ground pond, a wood frame with a rubber liner is easier to work with than concrete. wood gives you more attachment and sealing options if you want to put in a window.
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