Pond Green Up

Pond Green Up

Warm weather Algae again!!!

how we clear our ponds of algae.

 As soon as the weather starts to warm up most ponds "green up" in spring/summer with a dense bloom of panktonic algae. I get lots of calls asking what can I do to clear my pond?

Often the bloom is so thick that the water looks like pea soup  and the fish become totally invisible. 

For a natural control of algae blooms you have to look to competitors for vital nutrients in the water. The two nutrients that are highly correlated with algal blooms are nitrogen and phosphorus. 

Plants are good consumers of phosphates. The more vigorous the growth rate of the plants, and the more of them, the more effectively they will be able to compete with the algae for dissolved nutrients. 

If you harvest mature plants half way through the growing season by cutting them back, they will continue to be heavy consumers of phosphate in the water.

Most good nurseries sell a range of water plants, the hatchery wont start selling plants again till the new hatchery is finished.

Checkout the building of a hatchery photo gallery, we add new photos as we build.


The two  front ponds at the new hatchery setup in 2016/17 100,000 ltrs each with 100 large koi between the two, pea soup as soon as the warm weather hit.

We use a combination of both natural and mechanical to keep our ponds healthy and clear. The ponds have now been joined by a creek bed running between at the front.

On these ponds we have setup 4 x 55watt stainless steel UV sterilisers, we think we will need at least another 2 to keep the water clear.

Your other form of natural competitor for nutrients in the water, is nitrifying bacteria found in biological filters, they will compete for phosphates. The nitrifying bacteria that populate the filter have a high phosphorus demand. With correct filter media and cleaning processes a biological filter, can clear a pond very rapidly. despite the fact that it is a producer of nitrate.

Plants will also absorb nitrate, you will need a lot however to make a difference, the larger the pond the more you will need. Great with goldfish, but there is nothing koi like better than eating plants.  

In our pond filter there is not enough of the bacteria yet. You can expect a good amount in 6 to 8 weeks after setup. so long as you don't clean with tap water ,overfeed or over stock the pond in the first 2 months.

I have also put 4 1kg pond blocks in this pond to help build the bacteria and starve off algae. there are two sizes in these pond blocks, 1kg treats up to 50,000ltrs and 200grams treats up to 1000ltrs,.

You can also clear the water with algae killer, we have been selling this Australian brand for over 20 years and we know it works, for the instructions. Don't dose over the recommended amount, it wont work any quicker. 




For all ponds you will have crystal clear water in a week or two.

When you are cleaning water of algae, you are clearing the water, not the bottom or sides of the pond.

Algae on the sides and the bottom of the pond are a natural part of the environment, you will find a lot of your good bacteria living in this algae, the only way to get rid of this type of algae is a UV light unit. This type of algae does not cloud the water.


Windsor fish hatchery is not open to the public we are online only, we have moved to the central coast and are in the process of building a new hatchery for koi and goldfish breeding, This is a five year plan 2019 will be our third year.