pond filter/pump advice

[Mattyraby24]

Recently built a small raised pond 1200x1200x400 looking for some advice on a filtration system pump filter etc only looking to put half a dozen mirror/common carp in as fishing is a hobby of mine any advice would be appreciated thanks in advance.

 

[Mmathis]

Hello and welcome!

A lot of us here live in the USA, so we’re backward when it comes to metric conversions, so am embarrassed to say that I don’t know what size pond you are talking about . How many gallons (or liters)?

We are advocates of natural filtration with bog filters, where we let the plants do the filtration for us. That way you get not only a pond, but a garden as well! We can give you more information about this if you are interested or it sounds like something you want to look into.

As far as pumps go, you want something that will turn your water over about 1 1/2 times an hour. I can’t give advice on which ones because it’s not something I’m familiar with.

 

[j.w]

@Mattyraby24

 

[Mattyraby24]

Thanks for the reply, I believe if the convertor is right its around 84 us gallons, I have seen the natural filtration that you speak about but giving the limit space I have thats not really an option I don't think.

 

[mrsclem]

Just looked up mirror carp. These fish get big! 84 gallons is not going to work for a fish that size especially since you seem to be aiming for raising edible fish

 

[Phaewryn]

These measurements are in mm, yes? So, for the Americans, almost 4x4' square and almost 16 inches deep. It would have a volume of 576 liters or 152.16 US gallons. A mirror/common carp pond should be at least 4' (1.2 meters) deep, yours is a third of that. This little container pond is not appropriate for carp other than a couple of goldfish. A common general rule is 1" of fish per gallon as a starting point, but some fish need more than others and that's taking the size of the adult fish into consideration. All carp, including goldfish, need excellent filtration, being dirty fish, and since they are wide bodied, they need more like 2 gallons per inch. For the mirror carp you say you want, if that's really what you want and not a mistake, we can work this out, since they are also fat-bodied carp, like goldfish. According to https://www.cobhouse.org/fish-farm/common-mirror-carp/, mirror carp typically grow to be 10 inches in the first year, so if you are buying fry, you could raise seven mirror carp fry in your current container for a year, at which point they would then outgrow your pond and you would have to reduce the population to keep them under the 2 gallons per inch rule. https://aquapona.co.uk/carp-aquaponics/ says that when farming mirror carp, one should keep mirror carp at a density of less than 20 kg/m³. Your pond is about half a cubic meter, so you should stay under 10kg (22lbs) of carp at all times, and this recommendation is for a farming pond/tank with great filtration and aeration. https://www.cobhouse.org/fish-farm/common-mirror-carp/ says two-year old fish reach 4.5 pounds and three-year old fish over 10 lbs. Going by this, I would guess that you could keep seven fry for the first year, then you'd likely need to reduce it down to four or five for the second year, and then you would only be able to have two by the third year, and after that, only one, which would then likely outgrow your pond in five years, if not sooner. This is not ideal, because carp school, so need to be kept in a group of 2-3 to be happy, but that is in a pond that is the recommended size: I'm not sure they would ever be happy in yours since it is a third of the depth they really need. You would also need very good filtration, but that is complicated by mirror carp preferring still water. What it basically boils down to is that you can't do what you want with what you have. You can try, but doing it successfully is very unlikely.