Over the years industry has gradually added substances to our drinking water. Tin mining,farming, highway cleansing,lead and copper supply pipes as well as natural aluminium etc have all played their part in reducing the quality of water for our fish to live in.Fish were not designed to tolerate these levels of substances in the water that are usually seen to be safe for people. A major breakthrough in eradicating diseases to humans such as dysentery was made by introducing chlorine to our water supplies.Fish can tolerate only low levels of both free chlorine and chlorimine(fixed chlorine) The amounts of substances allowed to be present in tap water are set by the amounts that people can ingest safely without their health being damaged.We cannot expect the water authorities to supply water which is safe for fish as well as being safe for humans.We the hobbyist spend a great deal of effort supplying biological filtration,this is sometimes thought to be sufficient.Unfortunately this is not the case.Although certain types of bacteria can reduce Ammonia, nitrite and even nitrates they cannot reduce chlorine,chloramine,pesticides and herbicides or heavy metals.Free chlorine is the only one of these substances which can be gassed off by spraying.
Generally speaking aquarium hobbyists are more aware of problems associated with tap water than the
hobbyist who specialises in pond fish,this is probably due to the fish species being less hardy and more sensitive to
substances found in tap water than their hardier cousins koi .But this does not mean that our pond fish cope well with
the tap water containing these substances.This may not be immediately apparent until a fish becomes injured or suffers
from a parasitic attack or mild form of bacterial/fungus.It may become very difficult for the koi to heal naturally as it
will have to deal with living in an environment which is less than ideal causing the fish to be stressed and reducing the
koi's ammune system.
The safe or best fish levels of substances vary widely,However,low and high p.H levels,as well as soft and hard water,alter the effect of these substances on fish.As well as soft and hard water which alters the effect of metals on fish (see copper in diagram). As the p.H rises then there is more ammonia present in tap water,as the p.H falls then more ammonium is present.Ammonium is less toxic to fish than ammonia and it is more usual to find ammonium than ammonia in tap water in the U.K. However as some test kits read the total ammonia and ammonium and so without knowing the temperature and p.H of the water, the only acceptable level for fish is zero.It is interesting to see that fish and peoples safety levels coincide with nitrite but vary widly with nitrate.
It can be seen from the above diagram that it is important to know not only the condition of your pond water but also the condition of your tap water. It is on this basis I have submitted a list of necessary Checks in order to establish the condition your of water. However if the pond is of natural design and home to the more hardy type Goldfish then the frequency of these tests can be reduced and some tests omitted altogether.In this case it is probable that only p.H,Ammonia and nitrite need to be monitored.
It is also the opinion of many Koi keepers in the U.K.that the addition of rain water to the pond(Mostly unavoidable)is not of any advantage as usually it contains elements which are harmful to fish such as sulphur dioxide (acid rain),especially in towns and cities.Rain water which is usually saturated with these chemicals including CO2 (carbonic acid), is soft and acidic with no buffering capability and is of no use in binding up of harmful metals.
p.H.Test weekly minimum requirement. p.H can fluctuate dramatically during algae blooms( see 3.pH. and What Affects pH.)Pond fish will happily survive in water with a p.H. ranging from 6.5 to 8.5 (7.5 to 8.5 for Koi) but it must be noted that at a p.H. above 8.5 ammonia will be present (toxic),at a p.H between 7.5 and 8.5 a small amount of ammonia is present(also toxic) and at a p.H below 7.5 ammonium is present(relativly non toxic)
Ammonia.NH3Test weekly (minimum requirement).the first stage in the decomposition of fish waste and uneaten food in the formation of toxic ammonia and relatvely non toxic ammonium. Increase frequency of tests when filter or pond recently set up and has not matured,the pond is overstocked or when the fish have been overfed.
Nitrite.NO2Test weekly minimum requirement. Nitrite is the second stage of the nitrogen cycle see The Nitrogen Cyclewhich is produced by nitrosomonas bacteria. If there are any problems with the filtration in your pond nitrites is usually the first indication that there is trouble in an established system.Check your pond water more frequently if the pump has been stopped for more than a few hours.Or if any pond remedies (chemical treatments) have been added to the pond including salt)although salt will make nitrite less toxic to fish.
Nitrates.NO3Test not normally required but nice to have.Nitrates is the third stage in the nitrogen cycle and is produced from nitrites by nitrobacter bacteria. If Koi live in a pond environment without plants or vegetable filter it will be necessary to occasionally test the water for nitrates especially if the fish are being fed throughout the winter in a heated pond due to the reduced plant growth.In which case the removal of nitrates is achieved by small and often water changes.(nitrates can also be removed by revearse osmosis or by ion exchange resins)
Phosphates.PO3/4 Test not normally required but nice to have.Phosphate is a by product of fish and invertebrates metabolism and decaying organic matter such as dead algae and uneaten fish food.So in a established pond without plants or a vegetable filter the phosphate level will gradually increase to 1 to 5 ppm. Phosphates from fertilizers, pesticides and sewerage polute waterways and evetually end up in our tap water(Some water companies actually add phosphates to tap water to help reduce the amount of heavy metals) Due to these additions of phosphates in tap water, this prevents the reduction of phosphates in the pond by water changes(unless the tap water has less phosphates than the pond)It is for this reason that it will be benificial to know what the level of phosphate is in both your tap and pond water before carrying out any water changes. The best method of reducing phosphates in your pond is by increasing the number of plants in your pond or vegetable filter.
Hardness.Test not required but handy to have.(see 2.Water Analysis and Hardness.Only required if keeping Koi.As previously stated hard water is beneficial to fish in that it will bind up harmful metals(see copper in diagram).Hard water contains the permanent and non permanent salts of calcium and magnesium and it is these salts which supply a growth site for blanket weed.The reduction of blanket weed is often sought after by the discerning Koi keeper but this should not be achieved by completely removing these hardness salts from the water. It is usually achieved by reducing the available nutrients ( mainly nitrates and phosphates by the addition of plants or use of a vegetable filter.Hard water is also beneficial to fish as it reduces the load on the fishes osmoregulatory system see(4.Osmosis/Diffusion.).Some form of compromise is usually made by maintaining relatively hard water and allowing some growth of blanketweed on the pond walls(This gives a more natural appearance and also can provide some protection to fish during spawning).
Carbonate Hardness( Test not normally required but handy to have) measured in units of dH it is necessary to maintain a level of carbonate hardness no less than 2 dH as it is this carbonate hardness that stableizes the p.H ie buffering capabilty of the water or sometimes called total alkalinity see(p.H & what affects p.H.).
Chlorine/chloramine.Not normally required.Never allow chlorine/chloramine to enter your pond or filter Chloramine is free chlorine "fixed" into water with ammonium to prevent easy removal. We know that chloramine is more dangerous to koi than free chlorine.Chloramine (sometimes called total or residual chlorine in drinking water reports) has been found more widely spread throughout the U.K. than was first thought..It is probably wise to test your tap water for both chlorine and chlorimine as these levels can vary considerably(This test will also show if ammonia is present)However these substances can be rendered harmless by the addition of water conditioners before the water is added to the pond.
Oxygen.O2 Test not normally required .However it is sometimes necessary to test during the summer months. This is because the amount of dissolved oxygen is temperature related ie the higher the water temperature the lower the amount of dissolved oxygen the water can hold(saturation point) Many living organisms compete for this dissolved oxygen to sustain their life which include plants(especially during algae blooms), aerobic bacteria,decaying matter and fish.Unfortunately the fish are the least efficient at this process.It is a misconception that oxygenating plants remove carbon dioxide and add oxygen to the water.Whilst it is true during the hours of daylight,the oppesite takes place during the hours of darkness.It is therefore more accurate to carry out these tests early in the morning when oxygen levels will be at a minimum
Carbon Dioxide CO2.Tests not normally required.Plants and algae require CO2 for photosythesis as do nitrifying bacteria for cell construction.therefor a healthy biological filter is in constant dynamic equilibrium as old bacteria die and new bacteria form.thus,nitrifying bacteria compete with algae for dissolved carbon dioxide. High levels of C02 will cause problems with the p.H as CO2 reacts with water to form carbonic acid,causing the p.H to fall.Therefore it is necessary to have good airation to drive out CO2