dissolved oxygen      min 7-8mg/l

ammonia                   max  0.02mg/l

nitrite                           max  0.2mg/l

nitrate                         max 50mg/l above ambient tapwater

pH                         this is the measure of alkalinity or acidity of our water.koi acceptable levels are between

                              7-8.5 this measurement must be stable

                             pH1-7  acidic

                              pH 7 nuetral

                               pH  ALKALINE 

GH                        general hardness this is the concentration of mineral salts in a body of water.water

                               can  be soft or hard depending on this concentration

                                    10Dh the ideal for koi

                                     0-4Dh  soft water

                                     4-8Dh moderate to hard water

                                     8-16Dh hard water

                                     16+Dh very hard water

KH                  carbonate hardness (KH) alkalinity or temporary hardness,this acts as a buffering agent for

                       the pH levels by releasing carbonate ions when pH rises or falls

                         6Dh for koi

                                    1-2 too low

                                     4Dh minimum

                                     6Dh ideal

                                     above 7Dh too high at this level it can raise the ph of your pond water

temperature              koi have a preferred body temperature of 22-28 deg whilst this is what they would like they can survive at much lower temperatures if the decline in temperature is gradual say 1-2 deg per week as happens in our climate.Koi are best kept in the following temperatures in my experience

feb-march   6-8deg or ambient temperature

april -june  slowly raise temp to 17deg

july-sept     slowly raise to 22deg or above but not above 26 deg for more than 2 weeks

oct-jan        slowly lower to 12deg

the above is best achieved by a dedicated pond heater ,this information relates to fish over 2 years old.for fish under 2 years old it is advisable to not let them