Poor water quality is usually a result of the concentration of nitrogen compounds (nutrients) being too high. These nutrients are present in the form of Nitrates, Nitrites and Ammonia; natural, soluble chemicals, all present in equilibrium with each other in your fishpond. Nutrients are utilised in the growth of plants, but since your water plants have plenty of nutrients stored in the soil in their pots, the only plants excess nutrients feed are algae! This can turn your pond into something resembling pea soup! To understand how to reduce these nutrients, we must understand the natural process called the “Nitrogen Cycle”.

The main source of nitrogen entering your fishpond is in fish food. When fish are fed the correct amount of food, (enough to be eaten within 5 minutes) a lot of this nitrogen is absorbed into the fish for fish growth, and the rest is excreted by the fish as urea and fish waste. As fish waste decomposes, it releases soluble nitrogen into the water. If the fish are overfed, the excess fish food, rich in nutrients, will quickly foul the water, leading to fish deaths. Other sources of soluble nitrogen include leaf litter in your pond from over hanging plants/trees and waterplants.

To control the amount of nutrients in the pond, we must do several things:

Reduce the sources of nutrients:

• The number one rule to keeping fish is “Do not overfeed your fish”. Uneaten fish food is rich in nutrients and will turn your water foul very quickly and be detrimental to your fish’s health.
  
• Fish waste must be removed regularly. This is where a good pond filter will make your life much easier. Canister separate the solid waste, catching it in a sponge which can easily be washed out in a bucket of your pond water. By removing fish waste regularly, you are removing the source of much of the excess nutrients in your pond.
  
• Leaf litter must be removed periodically

Reduce the soluble nutrients in the pond

• Soluble nutrients must be removed. This is done by two methods. The most important being biological filtration. Biological filtration uses bacteria found naturally in your pond, which convert nutrients to non harmful forms which can be absorbed more easily by water plants. There are two types of good bacteria which undertake this process: nitrosomonas and nitrobacter. Both of these grow on every surface in your pond. Biological filters provide the good bacteria with a huge surface area to grow on, increasing their numbers and hence their ability to consume nutrients. To find out more about biological filtration, CLICK HERE.
  
• The other way of decreasing the nutrient concentration in your pond is to undertake fortnightly water changes of around 20%, making sure to use water de-chlorinator if replacing the drained water with tap water. Chlorine, found in common tap water, is extremely toxic to fish and must be removed from any water entering your pond.
  
• Dissolved oxygen another important element in your pond. The greater the oxygen content in you water, the healthier your fish will be and the more efficiently the good bacteria will convert nutrients to safer forms. Ways of oxygenating you water include the use of fountains/waterfalls, aerators, oxygenating plants and venturis.
  
• If your fishpond receives more than 3 hours of sunlight per day, it may turn green, even if you take all the above precautions. In this circumstance, your pond may require Ultra-violet clarification.