Many pond owners don’t realise this. That’s why they don’t react to algae growth until it’s too late. This is not only annoying, it makes it harder to achieve clear water for your dream landscape. We will help you to avert the classic pitfalls, so that you never have to cope with the situation.
The cause of tomorrow’s algae is in your pond now: phosphates (PO4). You will have noticed many changes in and around your pond in the autumn and winter. Plants died off, leaves fell into the water and quite a bit of sludge (a sediment layer) collected on the bottom. On top of that come other phosphate sources you don’t really notice: The phosphorus deposition into German waters is about 23,000 t per year (data from 2005, source: Federal Environment Agency). If you convert this value into a single square metre water surface, this equates to a phosphorus deposition of 2683 mg / m², which works out as a phosphate deposition of 8229 mg per m². For a 2 m deep pond in rectangular shape this would entail a phosphate load of 4.1 mg/l per year.
Like many other pond owners you have probably never vacuumed your pond bottom, even though excrement, dead leaves and food remains create a steadily growing sediment layer, which can’t be removed from the pond by the pump or the filter. Although this is biologically active, it is also a large reserve for the unwanted algae nutrient phosphate (PO4). That way a sediment layer several centimetres thick can release up to 0.6 mg phosphate into the water per day. In heavily over-fertilized waters values have been found as high as 12 mg.
But even with a clean pond bottom a large amount of phosphate can be dissolved in the water. It’s better to test with a fine scale phosphate test ( JBL PROAQUATEST PO4 Phosphate Sensitive ) the content in your pond water. This should not be detectable all year round, otherwise it could lead to large thread and floating algae blooms.
Algae and sludge already present carry phosphates, which are not measurable with a test. When they die off or release their nutrients these phosphates are available for new algae. This is why you always need to remove algae and sludge mechanically from large surfaces in order to completely remove the nutrients from your pond system.
As general prevention measure we recommend you vacuum up the sludge in spring and in autumn, check the PO4 content every 2 to 4 weeks, and continuously collect the newly created nutrients using a filter media ( JBL PhosEx Pond Filter ). Especially in springtime an increased entry of the unwanted substance is caused by pollen, blossoms and insects.
Generously planting your pond with bank-side and marsh plants, water lilies and floating plants will give the algae some competition for their nourishment. The remaining phosphates will be quickly used up to help the plants grow and your pond will look great all year round – a real feel-good oasis.