Carp growing on pond questions

Jonathan Robinson

Feeder Fish
Original poster
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Nov 2, 2016
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I was hoping that I might be able to pick your collective brains regarding an idea to grow on common and mirror carp on a very small scale, but commercial basis.

My background is that I love anything and everything aquatic. I have two aquariums (85 gallon and 170 gallon) with tropicals and a largish (3500 gallon) pond with mostly carp and a few koi. We're in Scotland, so a long way north for carp. I also go fishing a lot, for most local species.

We're intending to move to Germany in 2019 (thank you Brexit, though I am half German so it was always a possibility) and part of my plan to make a living is to grow on carp and import them into the UK for the purpose of stocking specimen carp angling lakes. Carp fishing is huge business in the UK, and large carp are very expensive but less so on the continent.

The climate is also massively more suitable for growing on carp than the UK, which has very cool and unreliable summers.

So the plan build what is in effect a large koi pond, but rather than using high tech filters, I'd like to use a reedbed/plant based filter.

The pond would be in the region of 50ft x 33ft x 7ft average depth (one end shallower and down to 10ft at the deep end). About 83,000 gallons in the main pond.

Bottom drain would feed a 12,000 gallon an hour pump which would feed a 50ft x 10ft reed bed (and other plants) filtration system. Deep gravel allowing long residence time for water within the filter system, with a water volume within the filter of about 12,000 gallons. So system volume 95,000 gallons. There would probably be a large UV clarifier before it reaches the reed bed.

So the question is, does that sound like a reasonable environment to grow on carp? Native mirrors and commons are considerably tougher than koi and also quite a bit larger (and hopefully grow quicker too).

The plan would be to introduce around 30 large carp (weighing on average 25lbs) and grow them on for one or two seasons. German summers are long and warm, and I'd expect the water temperature to be over 65 fahrenheit from May to October and over 75 degrees from late June to mid September.

With precise, but heavy feeding and what I regard as being a fairly low stocking density, what kind of growth rate would you expect on these fish (they will be quite a quick growing strain)?

The main issue that I foresee is that the carp will have come out of a natural lake environment where they will have been artificially fed, but a large proportion of their diet would also have been natural foods. They may spook in a koi pond and refuse to feed for a while.

I do intend to keep the water quality exceptional as I would intend to swim in the pool as well.

Any thoughts or ideas on the topic would be greatly appreciated. I've kept fish for some time, but this is a much larger project than I have yet attempted and I'm trying to establish whether it's viable or not.

I know that in a natural setting such fish (25lbs) can gain as much as 7lbs in a year. I'd like to think that this is possible (and not at the expense of the fish's health) in a tightly controlled environment like the one I'm proposing.

Thanks in advance.
 

Jonathan Robinson

Feeder Fish
Original poster
MFK Member
Nov 2, 2016
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Bumpety bump!

Someone must have some thoughts on the topic? From what I've read, your aquarists over Stateside tend to have larger ponds, and with the more extreme seasons (ie, in the UK we don't really have seasons) you're climate is much closer to that of continental Europe.

I'm just curious if folk think that I'd be able to achieve decent growth in a pond like that.
 

Jonathan Robinson

Feeder Fish
Original poster
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Nov 2, 2016
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Does nobody have anything to add regarding growth rates for monster carp? This is monsterfishkeeping.com after all.
 

Chub_by

Dovii
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Jan 30, 2012
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I do, but I bet you won't want to hear what I can add to the topic.. it all boils down to this not working IMO
 

Jonathan Robinson

Feeder Fish
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Nov 2, 2016
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I'm entirely prepared to hear that it won't work. I just need to know if it's worth the effort (beyond the recreational benefit of keeping huge carp) before doing any further research.

Fire away!
 
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Chub_by

Dovii
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Jan 30, 2012
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Well, for starters the expected temperatures you state seem very high, my pond is about the size of your current one, I am in a region of Germany with very warm summers and 75 will only be reached during certain hours of warm days, so in a system as large as the one you propose I consider that highly unlikely. One way around this could be to pump water into a very shallow (<1 foot) pond with a large surface area to heat it, but then we are talking even more additional costs, add that to the purchase and maintenance cost of a 12,000 gph pump and what it will cost to build a pond that size (which we don't have any info on, will it be clay? concrete? Liner) and you are looking at immense costs, considering how much carp go for even at large sizes.
Secondly where do you plan on getting (30) 25lbs carp? You won't find that many reliably in the wild, and they are very expensive in fisheries at that size.
Then the filtration; if you plan on having clear water for swimming in the pond, a reed bed will not suffice; you'll need lots of mechanical and probably some biological filtration. However if you do that, you will take away from potential natural food sources of the carp, which are important to gain fast growth (albeit you will be feeding).
However the biggest problem is getting them into the UK, shipping animals into the UK is hard enough as is ( been there before), but Brexit could complicate things even more. You are looking at getting them cleared by a vet here, quarantining them, and getting them cleared by a vet in England, not to mention shipping a 30lbs fish is hard and expensive in any case.

In the end it'll be a financial decision, can you make some of your money back off growing these fish on and have a great time doing so, sure, but will it be profitable? IMHO probably not.
 

Jonathan Robinson

Feeder Fish
Original poster
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Nov 2, 2016
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I really appreciate the detailed reply. The two areas of Germany we're looking at are bordering the hills of the Harz Mountains and the Eifel Mountains. We wouldn't be right up in the hills, but they'd be nearby (for climate reference).

My assumptions on water temperature are based on two areas of evidence. Firstly, I keep daily track of my pond temperature here in Scotland and it's always a couple of degrees above the average air temperature (day and night). The water just seems to soak up the heat rather effectively. Secondly, as a keen outdoor swimmer, I watch the reports for the water temperatures for the swimming lakes in Germany and they always seem to be well over 20c by July. A smaller body of water like the one that I'm proposing will be subject to greater variation in temperature, but I feel that it will heat up just a bit more than a natural lake. I may be wrong though.

I'd considered a tube pump for water circulation, though it's a type of pump I'm not familiar with. They seem to operate on large bore pipework, and don't like head. Low running costs though.

Pond lining would be simplest with a HDPE liner, but with concrete tanking to maintain vertical sides.

Good point on the filtration. Additional filtration could easily be added to system. I run a combined filtration system on my current pond, with a large pressure filter, vortex and 750 litre reedbed.

Sourcing the carp should be doable. I've seen them advertised at affordable prices from German fish farms.

The import is most certainly the most difficult aspect of the idea. I'm confident of being able to grow on carp, care for them and deliver them safely (which I'd do myself). The bureaucratic aspect of the venture is certainly the most daunting. I possibly have a little help with this.

Regarding the original question about growth rates, do you have any idea what kind of growth I might be able to expect with already fairly mature fish? Keeping in mind that carp on the Continent will naturally grow to 50lb plus without much additional feeding, I feel I ought to be able to bring them on from 25lbs to 35lb in a couple of years. Again, could be way off though.
 

Chub_by

Dovii
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Jan 30, 2012
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My pond will go to almost 30 degrees on a hot day, but like I said we have bad days too and fluctuation is high, also my pond is on a hill facing full south, both regions you are looking at are pretty cold (I went camping in the Eifel foothills in August 2015 and froze my ***off).
Also, remember that while our summers are of course better, winters here are colder and longer than in Britain - I don't feed my fish between the beginning of November and early to mid march in a normal year, that's 4 to 4.5 months! While in mild regions of the UK you can feed year round (I used to only miss a month or two of feeding when I lived in England)
Koi Keepers combat this by covering their ponds (which can get them up to 8 degrees Celsius) and feeding small portions of sinking food, however your pond would again be too big.
What farms are you looking to get the Carp from and which UK lakes are you looking to sell to?
The thing is, I know these UK lakes do seek large fish for instant gratification but AFAIK they source theirs from large farms in the UK/France, I doubt you could keep up with their prices on the small scale you are doing?

Regarding growth rates, that's the part I'm least doubtful of. While the 50lbs fish you speak of are mostly in highly fished lakes with a lot of artificial feeding(and are often stocked at large sizes), 10lbs in a few years is doable with very heavy feeding, good water quality and warm water. I know some carp breeders put 5lbs on each fish per year, although you have to remember luck is always involved (you'll need good genetics and weather)

What I'd like to know, does it have to be Carp? In or near the hills raising trout and sturgeon can be pretty easy and very fun.
 

Chub_by

Dovii
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Jan 30, 2012
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By the way, feel free to share pics of your current pond and inhabitants! I'd love to see them,Carp are majorly underrated here.
 

J. H.

Redtail Catfish
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Oct 14, 2016
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I am planning something like this, but on a smaller scale, 4x 1300gal US, but my goal is to take a family off the grid, not make a living. You should really look into aquaponics. It offers a second income, and much more powerful filtration than a reed bed. Also, I would consider adding a sump and/or a slow flow sand filter, as the weak link on most larger systems I see is a lack of biological surface area.
 
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