A clean pond
A clean and clear pond is not a question of coincidence. You obtain clear pond water by a proper biological equilibrium. Such equilibrium arises when the pond water has the right water values.
These pond values, namely the total water hardness (GH value), the carbonate hardness (CH value) and the degree of acidity (pH value) of the pond, can be simply measured and risen to the right level, if necessary. For example, if the pond water has a too low total water hardness and carbonate hardness, the oxygen producing plants will not properly grow en the pond will easily get turbid and green. The first step to clear water is testing it. On the basis of the test result you can choose one or more of the following measures:
Clear water is hard water
Hard water is a prerequisite for a clear pond. The water hardness indicates how many minerals are present in the pond water. These minerals are forming nutritive salts for oxygen producing plants. The joint hardness – the GH value of the water – is determined by calcium and magnesium. In soft water mainly floating algae are growing, no oxygen producing plants. The water hardness of every pond will decrease, because rain water falling the pond is extremely soft. Consequently the hardness of each pond has to be brought to level periodically. You can increase the hardness of the pond water by treating the pond with special means for the purpose.
Provide a sufficient amount of CO2
Oxygen producing plants provide clear water. For their growth these plants depend on CO2 in the water. Therefore you should see to it that there is enough CO2 in your pond. You can do this by inserting a biological filter, applying bottom substrate and proving water circulation. If necessary you can add extra CO2 to the pond by using special tabs.
Fight floating algae
Floating algae will cause green water. Fight floating algae by applying floating plants. Useful types include frog bit, duckweed, pointed weed, water star, water hyacinth and the azolla floating fern. These plants absorb many nutrients from the water and function as feed competitors for floating algae.
You can carry out all measures referred to at the same time: the more, the more effective and the sooner your pond water will become and remain clear.
Apply extra oxygen producing plants
You can carry out the aforementioned three measures at once. You should wait applying new oxygen producing plants till the pond will be more or less limpid again. For, if new oxygen producing plants should be applied in the water if it is not yet clear, there will still be to little CO2 in the pond water to let the plants grow well. Besides, floating algae are bulk consumers of CO2. To expedite this process, so that oxygen producing plants can be applied at once, oxygen will have to be added to the water with CO2 tabs.
If you will have applied these methods, your pond will meet the conditions for clear water again. Your pond will remain clear by continuing to proper water hardness, a sufficient number of growing oxygen producing plants and satisfactory CO2 production.