Thread: Pond Extension Advice Please

If you go for it, definatly go for the 2500g, 3000g would be better if you could persuade the OH

Many people reckon that to be about optimum. I don't think 10k ltrs would be worth the hassle.

15 kilos a month !!! that is a lot of food David,i use that in a season.

Definately go for the 2500 one,mine is 3000 gals and 4ft deep and 4mtrs x 3 mtrs and i am very happy with it size ways.
Fits in nicely with my smallish garden as you dont want it being an eyesore.
one bottom drain to drum to bio and shower and waterfall.

Would you have to move your bottom drain as it wont be entirely central if you extend,maybe if you can remove the top plate on drain and cut the liner round then silicone new liner on top of the old bit then put top plate back on top of the new liner,just a thought.
Seems a lot of waste of the old liner though.

Just another thought. Could you add an anoxic pond on as an extension. That would give you a greater water volume and can look really nice with lilies and other plants. Another advantage is that in the depths of winter you can bypass it and cut down on heating costs.

Big advantage - hopefully no need to dig up/disturb the existing pond.

[Just realised you have already done it with your goldfish pond ]

Have you visited any koi shows this summer? If you haven't, then I would highly recommend visiting a dealer who actually sells jumbo koi so both of you can appreciate how big these fish can actually get, and how much space they need to swim gracefully around in. Seeing the size on a tape measure doesn't really quite prepare you for seeing it in the flesh as it were.

I would personally not rebuild it to anything less than 3000 gallons, or I reckon it won't be the last pond build you will be doing in the next few years. They do say that we all need to build at least 2 wrong-ponds before we build the right one

The scary thing is that however huge the area seems when you mark it out on the ground beforehand, once it's finished and full of water you will generally be surprised how small it looks. I look at my 6k gallons now and think it actually looks quite small. Long term I think it will end up with around 10 full sized koi in it.

If you're worried about running costs, then I would pay a lot of attention to insulation and how you plan to cover it or enclose it in winter, since these days with eco pumps on the market it's actually the heating that is the major cost. If you're on a water meter then light stocking is the way to minimise water usage really. Building a smaller pond won't necessarily save you any water if you have the same stock in it because you end up having to change more water to make up for it.

Treatments can be bought in bulk for larger ponds, and if you stock lightly and are careful where you buy fish from this shouldn't make up a big proportion of your running costs. Food is definitely the other biggy- but again this is not about pond volume it's about stocking levels and growth potential of the stock you have, and also as a direct result of how much heating you do. Whilst you don't want to be feeding cheap rubbishy foods to decent koi, there is also no need to buy the most expensive foods on the market where most of the 'value' is shipping costs from Japan not the ingredients themselves.

That's my personal take on it anyway

Great responses so quickly, thanks all.

The consensus seems to be - Go big or leave as is.

Yes, it does look very big when marked out (as I already have an anoxic section on the existing pond which I haven't included in the quoted volumes.

But also yes I have seen 90+cm Koi in a huge pond which still looked too small for it and that has influenced my plans to extend. That said, I'd be more than happy with a couple of 60cm Koi.

If I increase length by 1.5 metres, which is the largest I can go because the fence is angled and the pond gets closer to it the more I extend) to give a volume of 11,300 that will mean the existing bottom drain becomes 2.5 metres from the furthest wall, which I think should be ok.

It is a shame about the existing box liner - less than a year old and proper quality 1mm thick, but I can cut it up and re-use it for a smaller application (such as the anoxic section).

The anoxic section is just under 1000 litres and could become a temporary home for the Koi for the 2 weeks it will take me to extend.

If I go ahead my plan would be to simply extend existing concrete footing then add 1.5m sleepers to the ends of the existing sleepers (dog-toothing them in situ) and then move the existing end wall of sleepers back 1.5 metres.

Another shame is the my pond cover was bespoke and the 2nd biggest expense of the existing pond, and it would now be too small.

All other pipework and filtration is at the other end of the pond, so it should be a relatively straight forward job. Digging being the most labour intensive part, new box liner being the most expensive part and bottom drain / securing sleepers being the highest risk part.

I like John's idea to cut existing liner around bottom drain and then seal new liner straight on top - Would this be considered a bodge job or will I get a reliable seal by effectively sealing 2 liners together and then screwing the ring back over the top?

If you use enough sealant and don't over-tighten the screws so you end up with a nice 'gasket' of the sealant under the ring then I don't think the old liner or sealant on it will matter too much. The most common mistake people make is over tightening, which squeezes all the sealant out of the joint. Leave plenty of curing time too.

Just a thought - I joined two liners together when I re did my pond. The join is along the top of the wall that separates my anoxic from my main pond. It would be perfectly feasible to join two liners together if all you are going to do is extend the length. You could even be a total cheapskate and re use both ends of the liner and add a flat section between them. It may sound dodgy but big lakes are lined like this with sealing of separate sheets of liner on site.

Think you maybe pushing it with 10 koi,the one you have just bought is 50 cm and the pool is 0.6 wide so not much room there,maybe a small holding pool and put half the koi in header pool and the rest in the other one and save the pond water,you could pick one up cheap.

Davej,was thinking of cutting the old liner and then connecting the new liner as normal on top of the old one with silicone then sandwich them with the top plate.

Are the cheap £30 pools good enough as a temporary home or should I avoid? Do you reckon this slightly pricier pool would be man enough to do the job:

https://www.ebay.co.uk/itm/Swimming-...53.m1438.l2649


Its big enough to hold most of my existing water and I'd buy a cheap pressure filter for the 2 weeks it will be in situ and add some mature media to it.

I can get all the footings in place before emptying existing pond, and even start digging at the far end, so fish will only be out for the time it takes to finish digging hole, fit liner and secure sleepers.

Digging by shovel takes longer than you anticipate, specially with stony clay, unexpected tree roots etc, but I reckon 4 cubic metres should come out in 6 days working alone.

Will keep Nexus bubbling away by adding ammonia and daily water changes - replicating the bucket experiment which worked a treat.

Bought this as a holding tank while extending pond (which will double up as swimming pool for the kids next summer). Slightly smaller than the first one I linked to but this is almost half the price of most places:

https://www.amazon.co.uk/gp/product/...?ie=UTF8&psc=1


Ordered some other bits including a 20k variable Jebao pump. Sleepers on order, requested quotes for the box liner (got a great price on the last one from KWB - Atlantica Gardens were a very close 2nd).

Will pick up some sand/cement this weekend ready to do the collar when weather is a bit less cold.

Then I can start digging up to say within 2 foot of the existing pond wall, after which I will try and get the whole extension done and completed with the Koi in temporary pool for just 1 week.

Not sure where to put the temporary pool though.... Could put it in garden but being only 65cm deep this could be a problem if temps drop suddenly, or could put it in the garage but that will be 6+ degrees warmer and could cause issues transferring the Koi back to the cold pond post extension. Any suggestions which might be the better option?

If the temporary pond is in a sheltered spot and you can cover it I doubt you will have a problem. You could always wrap bubble wrap round it if temperatures are looking too cold.