They are often overlooked, but having the correct water parameters is one of the most important factors to a successful, healthy pond. Providing your parameters are correct, your fish will be healthy, aerobic bacteria will be able to thrive and do its job properly and any pond plants that you may have will be able to contribute to the condition of your pond.
Correct Oxygen Levels in Ponds
The maximum amount of dissolved oxygen that can physically be held in water is 18.0mg/L. The minimum that you should let that figure get to is 6.0mg/L, anything lower than this and your fish will start to suffer. Some fish will be able to tolerate lower oxygen levels than this but it is advisable to try and keep the minimum at 6.0mg/L. Cold water can hold almost twice as much oxygen than warm water so keep a close eye on your oxygen levels throughout the summer months.
There are a couple of things you can do to maximise oxygen levels in your pond. Keep plenty of oxygenating plants, install a waterfall as this will bring in oxygen with the water and if needed, install an air stone or fountain to inject further oxygen.
If you need to make a partial water change for something, it is important to test your oxygen levels as tap water naturally has very low levels of oxygen in it.
What Should Pond pH Be?
Ph levels in ponds are very important but first we are going to have a quick chemistry re-cap on what pH is. Ph is a numeric scale that is used to determine the acidity or alkalinity of a substance, in this case pond water. The scale ranges from 1-14 with 7 being neutral, 1 being the most acidic and 14 being the most basic, or highest alkaline level. Battery acid has a pH of 1.0 whilst Lye (used in household drain cleaners) has a pH of 13.5, both can be just as dangerous as the other and give you a good indication as to why keeping a balanced pH level I so important.
Now that we have gone over what pH is, lets cover why it affects your pond, what it should be and how to change your pH level. A fish’s natural pH level is 7.4 so it is best practice to keep your pond as close to this level as possible. Fish can tolerate slight fluctuations in the acidity or alkalinity of the water but only down to about 6.8 and up to 8.2. When testing your pond’s pH level, be sure to test it twice in the same day, once first thing in the morning and once late in the day, preferably evening and preferably during similar weather conditions. The reason for testing twice is the algae that will be lurking in your pond. Algae is only active during daylight hours and when it is active it absorbs large amounts of carbon dioxide found in your pond causing your pH to read high. If your pH level looks a bit too high or low, you need to gradually bring it back down, you can do this by using Pond Equaliser.
It is crucial to keep your pH as neutral as possible. High alkaline levels in the water will increase the toxicity of any ammonia that exists in your pond, leading to possible Ammonia poisoning.
What are KH Levels?
KH is the measure of carbonate hardness in your pond and carbonate hardness is the amount of calcium carbonate in your pond. Calcium carbonates are very important as they feed the nitrifying bacteria that remove harmful ammonia and nitrates from your pond water. These bacteria are part of your ponds bio-filter, without this, your pond would be under great threat and would rely heavily on your mechanical filtration system. KH levels should be around 125ppm but they can fluctuate safely by about 20ppm either way.
Unfortunately, as with low pH levels and low oxygen levels, the effects of low KH levels can’t be seen by eye. You may notice that your ponds condition will deteriorate, Ammonia and Nitrate levels will rise and your pond will become more susceptible to pH swings which will ultimately lead to a pH crash!
Ammonia, Nitrites and Nitrates
Ammonia is released into your pond when your fish excrete waste. The nitrifying bacteria that are fed by calcium carbonate then break down the ammonia and turn it into Nitrite. Nitrite is then broken down further, to its final state, Nitrate. Nitrate is the final by-product of Ammonia. All three of these can be dangerous to your fish and should be monitored carefully. Ideally you should be removing any Ammonia in your pond to avoid it damaging your fish or breaking down further. Ammonia can cause Ammonia poisoning that can lead to death, Nitrites and Nitrates are not as dangerous but if your fish already have Ammonia poisoning they will be weak and susceptible to the irreversible effects of Nitrates.
Ammonia levels should be kept as low as possible, ideally at 0ppm but they can be okay at 0.5ppm if your pH level is neutral. Remember, the higher your pH, the more toxic Ammonia becomes so it is best practice to keep the level low. Likewise, Nitrites should be kept as low as possible around 0.25ppm but ideally at zero. Finally, Nitrate levels should be around 20-60ppm.
To summarise, water parameters are one of the most important things to monitor in your pond and they should be as follows;
Oxygen – Minimum of 6.0mg/Litre
pH – Keep your pH level as neutral as possible, around 7/7.5
KH – Keep your level between 95ppm and 150ppm
Ammonia – Should be at zero but can go up to 0.5ppm depending on the pH level
Nitrite – Like Ammonia, it should be as low as possible
Nitrate – Can be in-between 20 and 60ppm