Im thinking of doing the same & was told to get the best filter i can buy as there tend to s**t more than tropical fish

Oghh, i have some tiny carp and some tiny barble, as well as rudd and skimmers, they would be excellent in a tank, shame your a long way away!
If your using an undergravel filter make it deep, but it will still need cleaning a couple of times a year.
If you could have an external filter, you can still have a gravel bottom, but the filter will be dead easy to clean, some have reverse flow so you just reverse the flow down the drain. Get a filter double the size thats needed, thats my tip, carp are dirty fish, but very very active in warm water.
If you could get your external filter and pump though the wall to a garage or simerler, it would be even easier to clean out.

Ron

I started with the same intention a few years back, but I also wanted some silvers in there, too.

My tank is only 240L with an internal filtration system that sits in the back corner but above the gravel. As has been said, carp are dirty fish, but I would add that so are the skimmers, rudd, tench etc.

Also don’t bother with live plants, as my solitary carp (now about 6 inches) and two rudd (which have grown faster than the carp) demolish them within a few days. Every week or so, give them finely chopped cucumber of pieces of lettuce, which they seem to enjoy and it gives the additional vitamins not necessarily found in pellet and fish flake.

Once the carp are around 4-5 inches, don’t put any small fish in there. By small, I mean minnow sized, as the carp turn predatory and actively hunt the poor little things round the tank. Similarly with pond snails and mussels.

Be aware that the carp will grow too big for the aquarium in a few years, which is why I chose small Koi rather than commons and mirrors.

I also found that the tench rarely got a look-in at feeding time, as the water pig ate everything before the tench realised what was going on. The rudd are agressive enough to feed properly though, as are goldfish, but skimmers are a little shy, too.

Don’t forget to condition the water with a dechlorinator before adding your fish and I’d advise setting the tank up with water, gravel and artificial plants for a couple of weeks to start the equilibration process first.

When you clean them out, only change between 10 and 20% of the water at a time. Otherwise you can expose them to foreign/infective bacteria from the water you top up with. If they reach critical levels, they can damage or kill your fish.

To be honest i wouldnt bother putting carp in a tank as there very spooky fish and the minute you walk past it or go and have a look at them they will shoot round the tank in turn spooking the other fish in there.As said above if you want to keep carp then go fir koi,I keep trops,marine and koi.The koi are housed in a 6x2x2 quarantine tank before they go into my outdoor pond.I used to keep small mirrors and commons but as said above found they spook very easilly resulting in alot of stress to the fish they also grow at a rapid rate in a tank especialy if the water is heated.Good luck in whatever you decide to do,oh and whatever filter you buy you will still be doing water changes at least once a month as they are very dirty fish,hope this helps.

kept carp in a tank 6x4x4 for years no problems what so ever..under gravel filter and air pump..started off with tench and rudd at first but they soon fell by the wayside,ended up with the carp a wels cat fish and a pleco..thoroughly recommend sticking in a few gold fish/cheap cold water fish to start with to build the eco system up and yes a couple of the gold fish will die due to new tank syndrome…keep on thinking of setting up another one and just keep a pike perhaps i’ll get round to it one day..lol

One other point, Ron. If you intend to move your fish outside try to find out the origin of the carp/koi. If they’re from Israel, they will be slightly cheaper, but the chances are high that they carry KHV, which obviously you wouldn’t want to transfer to your outdoor fish.

If you want to keep coldwater species then fancy golfish would be the way to go Ron. I have reared small koi carp in tanks but have always grown them on in ponds as a tanked environment stunts their growth and can considerably shorten their lifespan. Cold water species of goldfish such as lionshead will require very good filtration and atleast 20 gallon of water per fish to be kept in optiomum condition. Tropical fish however would only require 1-10 gallons of water per fish.
Just another point Ron I hope your stand and flooring can support this load structurally as water weighs 10lb per gallon and a tank of the size you are talking of will weigh almost a metric ton when filled with water and added substarte and stone. If you do fancy keeping tropicals then I can give you some advice and refer you to other websites. In a tank that size you could have a very nice planted South American biotope or a Lake Malawi Cichlid tank.