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    Koi Keeping - Water Quality

    Provided you have purchased your first koi from a reputable source, you are bound to feel a sense of elation as you proudly watch your majestic new acquisitions lazily cruising the pond you have carefully prepared for them. But now your stunning centrepiece is at last complete, the responsibility of taking these beautiful creatures to the next level will soon start to weigh more heavily on your shoulders. You’ll have heard that nurturing koi carp is an ‘art’, and that professionals spend years mastering the secrets of breeding healthy fish which continue to blossom. So what are the priorities for a novice? And precisely where should you start?

    For koi, as with any other animal species, your first consideration must be to create and maintain a healthy environment. After all, prize bantams and scruffy battery hens alike will soon sicken and die if shut inside a dirty, rat-infested poultry house; but given good-quality housing, fresh air and access to clean ground, they will all flourish and bloom. Your fish are just the same, except your focus will be on what Japanese keepers call sui – the watery element in which your ‘living jewels’ will spend the rest of their days. Fish keepers say that ‘keeping koi is about keeping water’, and to keep your water (and thus your fish) in really good shape, you must first be prepared to delve into a little H2O-related chemistry and biology.

    Look after your O2 (oxygen) levels

    To keep your carp healthy and stress-free, you really need a minimum oxygen content of 5 mg/L. Your water can actually accommodate up to 18 mg/L of dissolved oxygen, and colder water is always capable of carrying higher O2 volumes than warm water. That means those hot summers day which raise your pond temperatures will also reduce the dissolved oxygen available to your fish. If left unchecked, this could soon trigger distress among your koi, especially in crowded, over-stocked conditions.

    The best remedy for low volumes of O2 is to create some form of turbulence because the resultant agitation will help to raise the amounts of dissolved oxygen in your water. The usual method of achieving the desired effect, and thereby satisfying the oxygen demands of your stock, is some form of aeration using either fountains or waterfalls, air pumps, or air stones placed in the depths of your pond.

    Aim for pH stability

    To create an optimum eco system for your koi, you should be looking to achieve a pH (power of Hydrogen) reading in the range 6.8 to 8.2. Whilst that means your fish will tolerate different acid/alkali profiles, they will not react well to fluctuating levels – so for fish health, the primary aim is always to create a pH within those limits which remains just as stable as you can manage.

    A word of warning: pH values employ a logarithmic system, so raising pH from 7 (neutral) up to 8 increases the alkalinity by ten, not just by one. And likewise, moving from 7 back to 5 – two places down the scale – will thus increase your pond’s acidity by a factor of one hundred (in other words, 10 x 10).

    It’s mostly about KH

    The secret of stabilising your pond’s pH levels is very closely tied to the KH rating of your water. A KH reading determines the alkalinity/carbonate hardness, which (chemically speaking) describes the concentration of carbonate and bicarbonate ions present. These elements function as a buffer, preventing sharp pH swings which can shock your fish and bring disease and death. Your ideal KH reading would be 105 ppm (parts per million) with a maximum deviation of 15 ppm. Anything beyond this range would suggest your water will be unable to safely absorb pH fluctuations.

    Where small adjustments are deemed necessary, adding white vinegar will increase acidity and lower KH readings, whilst introducing sodium bicarbonate in the form of baking soda will increase alkalinity and generate a higher KH reading. As a keeper, you will start to notice that the KH of your water will tend to drop slightly as your pond environment matures.

    Ammonia and the waste cycle

    The waste cycle is another chemical chain reaction occurring in your pond which you will need to understand and manage. Here, the ammonia excreted by your shoal of koi is first broken down by oxygen and bacteria to form nitrites. During the next phase, nitrites are then transformed into nitrates before then turning into free nitrogen.

    Excess levels of any of these elements can potentially harm your fish:

    • ammonia causes gill damage, and such burning will effectively prevent koi from accessing dissolved oxygen
    • nitrites will attack the kidneys and central nervous system
    • exposure to concentrated nitrates will eventually damage the immune system.

    Nitrites and ammonia pose immediate health risks, but accumulating nitrates can also become a potent threat if they are ignored. The usual recommendations for managing this potentially harmful trio of waste by-products are as follows:

    • ideally, your ammonia reading should be nil, though this is to some extent pH-dependent. Below a pH of 8, your fish may tolerate ammonia levels of 0.5-1 ppm – but only if the occurrence is very temporary
    • nitrites are also best eliminated altogether, though up to 0.25 ppm may be tolerated
    • you should aim to keep your nitrate reading within the 20-60 ppm range.

    A pinch of salt

    Salt has a reputation as a go-to product for treating a number of issues concerning water quality and the well-being of your fish. For example, it can help to combat the spread of algae, and protect against some diseases. Importantly, salt also helps your koi with osmoregulation – an internal system fishes use to balance and maintain the water content within their own bodies. Liquid concentrations in external aquatic environments will not match the levels found in fish blood, so pressure builds up at the interface between these systems. Salt helps to lower that pressure, which means your koi won’t have to work so hard to resist osmotic pressure, and will be less stressed as a consequence. A salt concentration in your pond of up to 0.5 per cent should be enough to cover these requirements.

    Creature comforts

    Maintaining a comfortable ambient temperature for your pond environment should be one of your primary management tasks. Though koi carp can tolerate a temperature range of 35-85 Fahrenheit, the optimum range is more like 65-75 F. Warm water causes more adverse effects than cold, chiefly because it holds reduced volumes of dissolved O2 and also exacerbates the presence of ammonia toxicity. The principal focus of your temperature control should be the avoidance of significant fluctuations.

    Chlorine watch

    Domestic tap water employs chlorine as a disinfectant, but it should not be present in your fish pond. Your koi will not find chlorine pleasant and its presence may indeed prompt them to take flight and try to seek purer water. Chlorine can damage the koi’s gill structure so they find it increasingly difficult to breathe. Other undesirable chemical elements may also be present in tap water, and the best advice is to install a tap-water filter system. Alternative solutions include dechlorination via the addition of purifying chemicals.

    In managing your koi-pond ecology, your overall aim should be to maintain consistency within the acceptable limits. That will give your rainbow-coloured residents every chance to adapt and live long, healthy lives.

    Last edited by admin; 12-04-2016 at 09:24 PM.



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