High levels of phosphate in pond water are the #1 contributing factor to an algae outbreak. Most of us treat an algae problem with algaecides– which is basically fine. The only snag, though, is that we are just treating the symptom and not the cause. To eliminate persistent algae outbreaks it’s essential we look at phosphate control.


  • As some of you know, phosphates are regularly added to our tap water in order to reduce pipe corrosion.
  • Non-Aquatic plant soil has higher levels of phosphate than Aquatic soil media.
  • Decaying leaves and debris that builds up on the bottom of your pond, creating a sludge, is a phosphate breeding ground.
  • Fish food contains the necessary nutrient phosphorus, which converts into phosphate once it has been excreted.
  • Run off from lawns and surrounding paving can wash in phosphates.


  1. Check your phosphate levels in your pond with a test kit such as Master Liquid Test Kit, or Refills for Master Liquid Test Kit.
  2. Check your tap water phosphate levels. If tap water is the culprit, you can top off your pond with rainwater collected from a storage tank. However, ponds should occasionally be topped off with tap water because it adds some essential hardness to the water. Be sure to use a Dechlorinator or Hose-end Filter when adding tap water.
  3. Use Aquatic Soil when adding or dividing pond plants Pondcare aquatic soil, microbelift aquatic soil. Aquatic plants in general are your best friend because they not only add much needed shade to pond water, but also slurp up the phosphates before the algae can. Be sure to remove spent leaves, as decaying matter leads to a spike in phosphates. To get rid of excess gunk, use a net or a vacuum. For in between cleanings use a sludge reducer such as Microbelift Sludge-away, Clarity Max, Pondzyme
  4. Feed your fish less rather than more. Use a high protein ‘growth’ formula during the Summer months, and look for a food that has a low phosphorous content such as Hikari Gold, Microbelift growth and energy, or Tetra growth
  5. Design, or re-design the edges around your pond to help prevent run off. Divert water from hillsides if it ends up in your pond.
  6. One of the most important things you can do is clean your filter or skimmer regularly. Backflush pressurized filters at least once a week, and clean out skimmer baskets. Doing this removes the phosphates that are bound to fine particles in the water. Use your beneficial bacteria consistently as this helps break down decaying matter.
  7. For instant, and continuous phosphate reduction use Microbelift phosphate remover or Laguna Phos-X granules.

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