If you have a small Koi pond with say 3000 liters with ten small koi, the koi will be fine for a couple of months or maybe years while they are reasonably small. As they grow however, the ammonia content will increase and the koi will get sick and die off and although this is a form of self regulating, it is not what you want in a pond. Don’t ever overstock your pond as you would loose koi and/or have sick koi at the same time.

You need minimum 5 liters per 25mm of koi length. Simply, you need 2000 liters per koi fish to be safe and not put ‘strain’ on the water, sand filter and bio filter systems. 10 000 liters five koi, 20 000 liters ten koi and so on.

Can you imagine your koi dying in their own faeces and ammonia? A horrible thought indeed, so prevent killing your (expensive) pets by following the criteria above. If your pond is over stocked, give fish to friends or cull the bad quality koi as cruel but necessary.