Water Testing – Phosphate

Phosphate is not dangerous to pond life. If you have high levels of phosphate in your pond it can be more of a nuisance causing major green water algae or blankweed problems. It will also provide a perfect environment for duckweed to thrive. This could be a nuisance for some people who would prefer to see their fish, or be favourable to others. Phosphate is usually used in fertilizes and it gives the same effect in ponds as it would in garden plants. It helps the algae and plant life to thrive.

Phosphate doesn’t have any adverse health effects. The major problem it could cause from the rapid growth of plants or algae, is when these eventually die off the decaying plant debris or dead algae will use up oxygen. So if you have low levels of oxygen in your pond and high levels of phosphate this could result in the death of fish from lack of oxygen, although this is rare. An issue people should be aware of is if you have a major blanket weed algae problem and decide to use a  concentrated chemical treatment to deal with it, make sure you try and get as much of the algae out manually as you can before and after treating it, and also make sure to have a pump going 24/7 as when the treatment kills that large quantity of algae it will drastically lower oxygen levels. The high levels of phosphate could also cause any liquid treatments for either the algae or fish, to be rendered useless. 

Phosphate can build up from a number of sources, these include:

• Garden Fertilizers
• Tap Water
• Fish Food - This is a major source of high phosphate levels in the pond, as most people tend to overfeed their fish and all that uneaten food will just settle in the bottom of the pond and release phosphates. 
• Run-Off
• Faeces
• Plant Debris

You can control high levels of phosphate by:

• Use high-quality fish foods and make sure not to overfeed fish. They won't need a lot of fish food as they have plenty in the pond to eat already. Feeding is also a seasonal thing. Most freshwater fish go dormant in winter or are just not as active because of the cooler temperature of the water and as they are not as active they don't require as much food.
• Have plenty of Pond Plants. Plants use the phosphate in the water and they can help the pond find an ideal balance. 
• Removing any debris from the pond.
• Make sure to use an aquatic potting mix when potting up plants for your pond. Normal garden soils can have high amounts of phosphates. 

You can drop in to The Pond Shop with a water sample and we can perform a Water Test for just $5.00. If you have any concerns or would like to speak to someone about a particular problem you are having with your pond you can send us an e-mail, give us a call or come and speak with us in the shop.