Fish Pond Water Quality More Advanced Topics
The following parameters are important if you want to have the very best water quality which will mean that your fish and your own pleasure will benefit enormously.
a. High levels of oxygen
b. Low variations in pH of the water
c. Good levels of carbonate hardness
d. The absence of pathogenic bacteria
The vital importance of Oxygen
Most of us in South Africa live in higher altitudes where the oxygen concentrations are lower than at sea level. This is why our cars go faster at the coast and we go to bed earlier in Johannesburg. If we lived at 12,000 ft we would get even more tired. On top of Everest we cannot breath without assistance.
Fish are like that and so are bacteria. Starve them of oxygen and they suffer just like us.
You cannot overdo the addition of oxygen or air into a pond. Most top koi ponds and filters bubble with air which is continuously pumped into the circulating water, the filter and the waterfall as well as the pond 24 hours a day 365 days a year.
There are some things you really do need to know about what happens to the oxygen concentration in your pond under different conditions. In this short discussion I will state matters factually and illustrate by numbers where I can:
a. Oxygen in water
Water can hold less oxygen the higher the temperature rise in the water. This means that in January (in the southern hemisphere where I live January is mid Summer) there is much less oxygen in a pond than in July when the water is much colder. This is why trout need cold water - they need high levels of oxygen which they cannot get in warm water. This is also why we have to drive 2 hrs + to Dullstroom to find good trout fishing.
Oxygen is introduced to water at the pond surface and by any mechanical means such as use of a fountain, waterfall or air pump etc.
During the last number of weeks in Johannesburg we have suffered from high temperatures and I bet many ponds have also.
At 10 deg C at sea level water can hold 10.9 mg/litre of oxygen. At 20 deg C it can only hold 8.8 mg/litre and at 30 deg C the saturation level is 7.5 mg/litre.
In practice very few systems reach these saturation levels and this is the reason Peter Waddington blows massive amounts of air into his pond and filter in order to get as close as possible to saturation.
Plants are always a good idea in a pond because they introduce oxygen into the water during the warmer parts of the 24 hour daily photosynthesis cycle. The higher temperatures occur during the day when oxygen concentrations would tend to be at their lowest due to higher temperatures. The plants however greatly assist by replacing any oxygen consumed by the fish/bacteria. At night however the plants reverse this process by using up oxygen from the water and converting it to carbon dioxide and then to carbonic acid. This is also another reason for maintaining pump flow 24 hours per day so that circulating water continues to pick up oxygen during this night time period and provides new sources of oxygen to compensate for that taken up by the plants.
Last time I made the point that in ponds where high levels of algae existed then these algae could totally deplete a pond of oxygen overnight causing total fish loss.
In summary you cannot overdo the introduction of air into a pond. Blow, blow, blow if you want to.
b. pH and the Pond
In a swimming pool if you measure the pH at noon and again at midnight it will be the same. In a pond with plants it will not be the same because of the photosynthesis cycle. During the night the pH will fall before rising again during the day to its original level. With high levels of algae the pH can change dramatically with dire consequencies. Do go to http://www,garden-pond-algae.com
pH is a measure of the acidity or alkalinity of water. The measurement scale is from 0 to 14. At the mid point of the range the water is neutral since the acid and alkali balance each other which is the case for pure water. Less than 7 the water is acidic (vinegar is less then 7, a lemon is about 2.2 ). More than 7 and the water is alkaline (sodium carbonate is a good example and milk is between 7.1 and 8.5).
Stable levels of pH are desirable and a range between 7 and 8.0 is good for a pond. When you start seeing levels of 9 there is a danger developing.
It is not a simple subject however to talk about pH even though it is simple to measure. The reason is that pH has a great influence on almost everything in a pond environment. It effects how the biofilter works, it effects the fish, it in turn is effected by the addition or removal of pond water and whether the water from the tap in your region is hard or soft. At higher pH levels toxic levels of ammonia become very deadly.
To have a high level of control over pH fluctuation it is very important to have a good level of hardness in the pond.
pH and Water Hardness
To minimise the natural pH fluctuations in a pond it is very important to have a good level of hardness in the pond. What is this hardness?
When you wash your hands in water and you find it difficult to get a good lather (even using Dove soap) you are in an area where the water is naturally hard. Conversely when the water feels slimy when you wash your hands the water is called soft. Where I live some 15 kms east of Johannesburg the water is probably in between.
Hardness in water is caused by high levels of dissolved salts and particularly magnesium and calcium salts.
There are also 2 types of hardness - permanent hardness and tempoarary hardness. Water which has permanent hardness has a lot of magnesium and/or calcium SULPHATE salts as well as some other salts. Temporary hardness is due to magnesium and/or calcium CARBONATES. If you look inside your kettle you might see deposits of white or grey solids on the heating element. This is CARBONATE coming out of the water when it is boiled and this is why it is called temporary.
CARBONATE hardness is very important in a pond in order to control pH.
The total of the SULPHATES and CARBONATES in water is called permanent hardness or TH for short. The amount of CARBONATES only is called temporary hardness and is referred to as CH for short.
Total hardness (TH) is important for the good physiology of fish.
The following is what happens in a pond which has a low level of CARBONATES.
During the day any plants (and this includes algae which is a plant) in the water remove this small amount of carbonate and as a result the pH of the water can climb significantly and maybe even reach a level of 9. At this level ammonia secreted by the fish themselves is EXTREMELY poisonous to fish and your fish can die - under these conditions your fish will appear very distressed, gasping for air, lying on their side, lethargic and so on. If there were higher levels of CH in a pond it would be impossible for the pH to rise to 9 and it would also remain a lot more stable which is much better for fish.
If you suspect ammonia poisoning then immediately test the water for ammonia. If the test proves positive start changing some of the pond water immediately (say 50%) and DO NOT feed the fish - fish can live happily without feeding for days on end. Keep changing portions of pond water until you are able to stabilise the situation. Keep measuring the ammonia levels in the water.
Think of CH as preventing pH from fluctuating widely and reaching dangerously high levels. This is good for fish and plants in a pond. That is all you need to remember.
Good levels of TH in a pond are 7 to 14 degrees
Good CH levels in ponds are 6 to 12 degrees
The only way you know if you have the correct levels is to test the water yourself by buying a suitable test kit or take a water sample to a fish outlet with these testing facilites.
If you find the hardness is too low then select a product from the shelves to correct the problem and follow the instructions carefully.
It is also a good idea to test your tap water to see if it is hard or soft so you can forecast what might happen over a period of time.
Acceptable Values For Pond Testing
Ammonia: Nil
Nitrite: less than 0.3 mg/litre
Nitrate: 25-100 mg/litre
pH: 7.0 - 8.0
CH: 6 - 12 deg CH
TH: 7 - 14 deg TH