Koi Ponds

The worst of these is Crassula helmsii, the New Zealand pygmy weed.  It is also called Tillaea recurva.  It is light green, will grow in damp ground and under water to quite deep levels and will just fill a pond completely.  It is still a plant, so it still provides habitat for invertebrates and so on but it does out-compete native plants and does not support as much wildlife as native plants.  It is very troublesome.  Once you have it, it is extremely difficult to get rid of other than stripping the whole pond completely back to the liner and starting again

Key things with fish are to avoid stocking too many.  If you really pile fish into a small pool it  simply becomes overloaded with nutrients and it will go green and unpleasant.

Koi can be an issue.  They grow very big and eat a lot of food and they are not very keen on Scotland’s cold climate.  They sometimes do quite well but they are probably better of further south.

Golden orfe are a fish I like.  They seem to like cold water, they are visible, they shoal, they breed and they live for a very long time.

Goldfish and shubunkins are also fine.

There is no point in having fish like tench.  You simply will not ever see them and they just do not perform any more useful function in a pond than goldfish would.

Fish tend not to mix very well with other wildlife, simply because they will eat a lot of it but you do get frogs using fish ponds quite successfully and a small number of goldfish or orfe are a nice addition to a small garden pond.

We are often asked to build wildlife ponds.  It is a relatively straight-forward job and you do not need a huge amount of depth.  The key thing is to plant them heavily with native plants – such as bog bean, hornwort, water mint, marsh marigold, purple loosestrife, flag iris – all provide flower for bees and generally habitat for invertebrates.

Sometimes wildlife competes.  It is a very natural situation but adult newts, for example, will eat frogspawn.  However if you just create shallow areas with native plants and leave it alone, then, as they say – build it and they will come!

No need to take silt or water from any other water course nearby; that is often a mistake because often canals or the local pond actually have alien things like Elodea in them and you simply introduce them into your pond.  Much better to buy native plants or get them from somewhere that you know is clean and then all the other invertebrates will colonise anyway.  Frogs, newts and sometimes toads will find their own way to your pond.  I personally do not see much wrong with taking some frogspawn from where there is a lot of frogspawn, perhaps from your local park, and putting it in your own little wildlife pond.  Supposedly you can transfer diseases and so on, but given that the adults spread out all over the place anyway, I cannot see much of a problem and you will get an instant population of frogs.

Small, formal, falls of water, for example water falling from height from something like a stainless steel letter box are much more difficult to do than they look.  The fact that you have a small reservoir of water at the bottom means that any water loss – a splash, a slight mistake in any of the work – and the bottom reservoir just drains rapidly and you have to keep filling it up.

Because you cannot generally plant them, keeping the water clear can be difficult. You either have to put UV’s and, perhaps, dosing units on them to keep them clean or you have to find some way of introducing plants.  These features look fairly simple, but unfortunately they are not.