A new pond must settle down -six weeks is not an unrealistic time to wait -before introducing fish.
During the first couple of weeks the fresh water in the pond will turn a browny-green colour, and become progressively cloudier as micro-organisms multiply.
A variety of plants should be in place, including plenty of submerged oxygenators.
These will help to absorb dissolved minerals, and of course provide oxygen to the water.
The fish will be afforded some protection by these, and will also use them for green food.
Floating and deep water plants provide the shade which is very welcome on hot summer days.
By the sixth week the water should be clear.
It is worth remembering that most fish scavenge.
They'll nose around and disturb freshly planted aquatics, so it is important to allow the plants time to establish before the fish are introduced, and to cover the soil in the pots with a thick layer of gravel, otherwise the soil will be displaced, and the water will turn brown.
Buying some fish from a garden centre, transporting them home, and then putting them in the pond, with no forethought about the environment they were in, and the one to which you are now subjecting them, can result in a high, if not total, mortality rate.
So, to start with, it is essential to know just how many fish, and of what size, your pond can accommodate safely.
Work this out before you start spending money Fish make great - and comparatively undemanding -pets for children on buying the fish.
Of course, you may exceed the recommended quantity of fish under certain conditions if, for instance, you have a pond that is very deep, or you have installed an over-sized filtration system, but this is unlikely for a beginner to the hobby.
The best time to stock a new pond, or add further fish to an existing complement, is in late spring or early summer when temperatures are fairly stable but, when buying fish you do take a bit of a gamble.
No one can say with 100% conviction whether a fish is absolutely free of disease or parasites, regardless of how healthy it may look.
This six-point plan for detecting signs of a healthy fish should serve as a useful guide: 1.
LOOK FOR A LIVELY DISPOSITION.
Fish such as goldfish, orfe and koi should be constantly on the move, and even dart about when 'spooked'.
If they seem lethargic, or float on the surface, or lie relatively still at the bottom, then they are best avoided.
However, note that bottom-dwellers, like tench, should be at the bottom and they move quite slowly -this is normal.
CHECK THE FINS.
A healthy fish should have its fins well extended.
The fin on the back (the dorsal) regularly extends and collapses as the fish hovers or changes direction; it is usually collapsed as the fish moves its tail fin (the caudal) to propel itself forward.
Any damaged fins will indicate that the fish has been in a scrap, and it should be avoided.
LOOK AT THE BODY.
Damaged or missing scales are unsightly, but not necessarily a sign of ill health.
Scales can usually regenerate without subsequent infection.
However, if there any blood spots, or fungal growth (looking like cotton wool), then do not buy it - or other fish from the same tank.
EXAMINE THE EYES.
A healthy fish should have clear eyes.
If they are 'milky' in appearance, it is a possible sign that the fish is injured or otherwise unhealthy.
This can be difficult if the fish you want is moving about quickly, or hugging the bottom of the tank, but it is worth taking the time to find out.
CHECK THE COLOURS.
The scales of a fish are covered by a protective layer of mucus, which tends to enhance the colour of the fish and make the body bright, vivid and clear.
If the fish is unhealthy, there can be a check to the mucus, or an excess in the production of mucus, both of which can cause the appearance to be dull or cloudy.
OBSERVE THE SWIMMING TECHNIQUE.
A regular pace, in straight lines, and in a considered way.
This is how a healthy fish should swim.
It should not roll about, or lose its balance, or keep floating upwards, or sinking downwards.
The one word of caution here is if a fish is eating, or has just had a meal, it can sometimes sway as it chews.