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Thread: Galvanized stock tank 300gallons

  1. #1
    Nisai An Ly's Avatar
    Join Date
    May 2007

    Galvanized stock tank 300gallons

    Any one use these for quarantine or raise small tosai
    its galvanized metal, not sure if there is any ill effects with metal
    but holds about 300 gallons and it's oval shape as oppose to rounds which takes up too much space
    8ft L x 3ft W and 2 ft deep $250
    Last edited by An Ly; 08-29-2017 at 01:54 PM. Reason: Typo

  2. #2
    Nisai An Ly's Avatar
    Join Date
    May 2007

  3. #3
    Daihonmei MikeM's Avatar
    Join Date
    Dec 2003
    Orlando, Florida
    Galvanized stock tanks have long been used successfully to raise small fish of various types. Koi, however, are particularly sensitive to metals. This has caused some to recommend against using galvanized metal with koi. Others using galvanized stock tanks for short term purposes report experiencing no problems.

    The galvanized tanks which have been discussed on the boards have been galvanized steel, which is much cheaper than stainless steel. However, with all the metal recycling occurring around the world, I expect there are 'mixed metal' galvanized tanks around. These could have potentially harmful metals other than the zinc coating.

    I am not aware of a definitive treatment of the subject of zinc in relation to keeping koi. The main concern is that the zinc coating on galvanized steel will release zinc into the water and that the zinc will compromise the immune system. In moderately hard, alkaline water (pH 7.5 and up) the rate of zinc release is supposedly quite low. In soft acidic water, the rate of release into the water is higher. However, the harmful effects of zinc in the water seems to increase as the pH increases. That is, it leaches into the water at a slower rate, but what is released has a more harmful effect as the concentration rises. A lot of different interactions become involved, which makes it difficult to say much that is reliably useful.

    Given the need for a high rate of water changes when using a stock tank, there is likely little risk of harm as long as the water has moderate hardness and pH. Long term, stock tanks are not suitable for koi because the koi will grow too big for them and there are studies indicating that zinc can have negative effects on growth and development of fish even if not fatal, but it depends on many interacting factors. In some instances, the negatives took extended periods of time to be observed. Mortality studies indicate that rather high levels of zinc are required to kill a koi, but these look at short periods of time and are not useful when considering a permanent, continuing exposure. I recall a koikeeper in Holland who had a galvanized screen in the pond which seemed to retard algae growth with no adverse effects on his koi. However, the small amount of screening in a large pond is not comparable to a galvanized 'pond'.

    If you are going to use the galvanized tank, I suggest you fill it with water and let it sit for a week or two to allow excessive zinc to leach.

    Personally, I would spend a little more to get plastic and avoid the concerns.

  4. #4
    Nisai An Ly's Avatar
    Join Date
    May 2007
    Thanks Mike, for your expertise, much appreciated. I think I'll just look for something else.

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