(Validation for the choice of 0.5 mg/L as an achievable, safe total ammonia level in unfiltered vats)
Research has shown that long term exposure to free ammonia (NH3) levels below 0.02 mg/L do not cause harm to fish. In c1992, OATA produced a table of ammonia values for a wide range of pH and temperatures. If the total ammonia level (most test kits only measure total ammonia) is maintained below the level indicated on the table for the appropriate pH and temperature, then the free ammonia level will not exceed the safe level of 0.02 mg/L. This table should be adhered to in koi ponds and in all other biologically filtered systems where the exposure of fish to that level of ammonia is continuous. The OATA table was designed to cover the varied situations existing in ponds and aquaria of all kinds. A similar table has been calculated to cover the range of pH and temperatures appropriate to koi keeping, and as a result, this new expanded koi-specific table gives more detail in this range. Both tables were calculated from original source data published by Liao (1972), which was refined by Spotte (1979) and further refined into a four figure accurate data set by Kordon (date unknown, circa mid 1980s). Both the OATA and the new koi-specific table were calculated by slightly different mathematical methods and show close correlations in the areas where they intersect, therefore both tables mutually validate each other and are suitable to be used as a standard in biologically filtered systems.
Koi will tolerate short term exposure to higher levels of ammonia without harm. Values from the OATA table or from the koi-specific table are unachievable at koi shows when the local pH and water temperatures are high. In these situations, a more realistic value of total ammonia is desirable.
Fish welfare. By Edward J. Branson: MRCVS, Veterinary Surgeon, RCVS Specialist in Fish Health and Production. Monmouthshire, UK.
States that: “Thurston et al (1981) reported that test fish tolerated constant concentrations of ammonia better than fluctuating levels”.
(It is therefore better for koi welfare at koi shows to adopt a sensible and achievable level, albeit a little higher than values obtained from ammonia charts, rather than conduct excessive and repeated water changes in an attempt to achieve unrealistically low values).
Effect of dietary protein level on excretion of ammonia in Indian major carp. By Chakraborty & Chakraborty: Department of Fisheries Technology, Bangladesh Agricultural University, Bangladesh 1998.
Rupert Bridges quoting Chakraborty states:
“at 20°C unfed common carp produce around 87 mg NH3 per kg bodyweight per day”.
(An unfed Asian carp is the nearest analogy to koi carp under show conditions).
Koi body weight from weight calculators:
Manual confirmation of body weight (good fit):
Typical koi show example at a venue where pH is 8.5 and temperatures are 22°C to 25°C:
2.8 m vat stocked with 4 average size 6 + 4 average size 2 and with water testing every four hours
Average size 6 weighs 5.754 kg
Average size 2 weighs 0.453 kg
4 x average size 6’s: 23.016 kg
4 x average size 2’s: 1.812 kg
Total body weight in vat: 24.828 kg
A 2.8 metre vat contains 2464 litres of water at show depth.
Unfed carp excrete 87 mg ammonia per kg body weight per day.
That is 3.625 mg ammonia every hour per kilo body weight.
24.828 kg of unfed carp excrete 90.0015 mg ammonia per hour
90.0015 mg in 2464 litres of water raises ammonia level by 0.0365 mg/L
(Therefore: 4 average size 6’s + 4 average size 2’s raise ammonia in vat by 0.0365 mg/L per hour).
Initial dumping after release from the travel bag.
Ammonia from food or from koi feeding on algae and aquatic insects etc. prior to show.
If the showground pH is 8.5, and temperatures range from 22°C to 25°C then the maximum allowed total ammonia from the OATA table, (or koi-specific table), is between 0.16 mg/L and 0.13 mg/L.
(Aveley pH is 8.5, Newark up to 8.7, Aveley has reached 25°C, Newark has reached 22°C).
Table of total ammonia values in 2.8 metre show vat with 4 hour test regime in relation to target maximum levels for:-
Aveley showground; 8.5 pH and 25°C applied to OATA table = 0.13 mg/L
Newark showground; 8.5 pH and 22°C applied to OATA table = 0.16 mg/L
Safe, achievable alternative; 0.5 mg/L