Goldfish, Koi And Ponds...

[Tokis-Phoenix]

Ok, im hoping to get my pond built within the next fortnight/couple of weeks (i'm waiting for a call back about if and where there are any gas pipes or electrics running through the garden- i've checked about water pipes as well and apparently they won't get in the way of the plans), so all is running smoothly at the moment .
One of my neighbours who has experience digging ponds is going to help me dig it (there are some friends who also may be able to help out) as i'm going to need some helping hands digging with all the thick clay that my back garden is. I will probably encounter tree roots (there is a massive birch tree in the garden as well as an australian tree one of the ponds is going to be close to), but i'm hoping they won't alter the pond design too much "fingers crossed".

Overal, there are going to be 2 main ponds in the garden, both connected by two channels so the fish can swim between them, there is also going to be a small pond for nature as well. I'm aiming to have an organic wildlife-friendgly japanese style garden eventually.
As far as the fish go, i already have two goldfish (a comet and a common goldfish, both orange) in a 30gal that i adopted some time ago that i want to put in the pond when its done, my fiance's parents are also selling up their house right now and i will also most likely be adopting their remaining goldfish in their old pond (they used to have many koi carp and goldfish, but cats and posibly a heron made short work of them over the years), they say there's about 7 small goldfish left. So at the moment, the pond is looking like its going to turn out very goldfish orientated.
I would like some ghost carp (or ghost koi as they are sometimes known, i believe they are hybrids between koi and a particular type of carp, they apparently grow smaller than koi and are hardier) in the pond, but if normal koi are still an option i would like some normal koi as well on top of the goldifsh and ghost carp. I'm also open to other posibilities of coldwater fish like tench if they'll fit the pond/habitat well and tolerate the cold winters down here.
The pond dimensions are a bit rough right now as we don't know how much we'll have to modify the pond shape due to tree roots and so forth, but right now i am planning on having one pond that is about 7-8ft wide & long and 4ft deep, and a second pond connected to it that is 6-7ft wide & long and 3ft deep (it may be deeper if the digging isn't too hard). Both ponds will be connected by two channels about 2ft wide and 2ft deep, there will also be a third non-fish pond about a metre long/wide and 3ft deep for wildlife.
I'm not sure how many gallons the main pond system will work out to be, but i think it should be fine- i don't want tons of fish, and i'm sure the current one's will probably breed anyway. I havn't looked very thoroughly into filtration/pond pumps and things yet, but will do so soon.

But i have often heard people saying that you shouldn't mix koi and goldfish, what reasons are there for this?

 

[black angel]

I think the main reason is size difference. Koi as you know can get to 3 feet and easily eat goldfish. Ive seen ponds where there are both types but they are at the same size. Ive only seen big koi with huge goldfish so it must work.
As long as the pond for the koi is four foot deep which it is then you should be fine. Stocking as well may limit if you have koi as they need 250 gallons each.
I like the idea of the channels between ponds but for disease outbreaks it might be a nightmare to treat if the total area is huge.

 

[bribones]

my pond is 12x6@4ft deep and i keep a mixture with no problems so far but as the koi grow i will be removing some of the smaller goldfish to allow for the growth of the koi,koi tend to be more destructive than goldfish and slower swimming types arnt recommended ,try to keep the sizes similar but dont add small fish in with large as they will become livebait,also dont add too many at once you need to allow the pond to adapt to the stock,my advice would be to be selective ie koi only or goldfish only

oh and good filtration is a must with koi and with a split pond you might end up with a few problems to sort out

hi angel

 

[Tokis-Phoenix]

Thanks for the info, will koi be alright then if i buy small koi about the size of the goldfish so the koi are too small to eat them? Are their growth rates similar at all? As far as filtration goes, if i cannot find one system powerful enough to run the whole system, i'll stick a pump/filter in each of the two ponds, which i hope should work out ok.
I really don't have much of an idea as far as filtration/pumps go, i don't know where to start really or what would be simplest and easiest to run for my pond? I read that koi eat pond plants, are their any robust plants they won't be able to destroy or any plants that will thrive enough in a koi pond? I would like lillies and some general pond plants to add some green to the edges and depths of the pond as well .
The only bad thing is a got a call back on the electrics, and they say thats there's an electrical mains or something in the garden so they are posting the details, so i will have to wait for that info to arive as well as info on anything like gas pipes before i can go ahead.