8 tips for Green pond water for the outdoor fish pond

May 16, 2022


Firstly, it must be said that outdoor fish ponds are not sterile environments like a swimming pool.

Garden ponds are full of life and we aim to encourage the fish pond to be biodiverse on the macro and micro scale, in order to maintain a healthy balance, which will result in clear water, healthy fish and water plants.

It will also require less pond maintenance!

Water plants, algae, bacteria, insect larvae, worms, tadpoles, frogs, fish, and crustacea are all part of the mix, so we shouldn’t get too alarmed if we see a bit of algae in the pond as this is a natural part of the ecosystem.

As much as we do try to emulate a natural environment, backyard fish ponds come under pressures that are generally not seen in natural ponds under normal conditions. Garden ponds are often stocked with higher fish densities than what we would expect to find in nature and that increase in nutrient levels can lead to out-of-control algal growth.

We can have an expectation of crystal-clear water, but not an algae-free pond. Algae will grow naturally as a film overall submerged surfaces of the pond and help to both provide oxygen to the water and remove nutrients from the water. This is part of the healthy pond environment. So relax!

There are 8 ways to ensure that our pond water does not go green with algal blooms.

All ponds are different and so we recommend utilizing a balance of the following to suit your needs

1) If you live in a region that experiences hot seasons, try to build your pond in an area that will have at least some parts of the pond partially shaded during parts of the day. Algae requires sunlight to thrive and warmth in the water, so ponds that have at least partial coverage experience less severe algal issues.

2) Reduce the sources of nutrients going into the pond. Without nutrients, algae will not grow. Nutrients will enter the fish pond through two main pathways: Fish waste and leaves degrading in the pond. Ensuring that the pond is not overstocked with fish, they are not overfed and leaves are regularly scooped out of the pond, will reduce the nutrient load.

3) Have the correct sized pump and filter on your fishpond. There are a few different types of pond filters to choose from that you will read about, such as pressure filters, gravity filters, in-pond filters and natural ecosystem filtration.

We recommend that you get in touch with your local pond specialist so they can guide your through what is best for your needs.

The Fish Works has been experts in pond filtration for fish ponds in Australia for over 30 years and can help you find the right solution for you.

4) Do water changes. Water changes dilute the amount of nutrients in your pond water. Don’t just pump the water down the drain though, as your garden plants will love to be watered with this liquid gold!

5) Have lots of water plants. Water plants directly compete with algae for both light and nutrients. They look great too!

6) Test your pond water for pH, ammonia, phosphates and nitrates. We recommend at least monthly testing of pond water to ensure that the parameters are within healthy ranges. We would like the pH to be between 7 and 8, Ammonia to be 0.5 or less, phosphates zero and nitrates less than 50ppm but closer to 20ppm (or even zero!) to have less algal growth.

7) Use pond treatments. Regular additions of natural algae treatments such as beneficial bacteria can often tip the balance in your favour in terms of reducing algae in ponds. Phosphate-removing chemicals bind phosphates and drop them out of solution, making them unavailable for algal growth.

8) Avoid using harsh algaecides where possible. Algaecides will clear up green pond water, but the problems with them is that they do not address the cause of the issue, only the symptom (green water) Algaecides will kill algae, so your pond will then have lots of dead algae in it, which will cause nutrient levels to rise and oxygen levels to drop. Then the whole cycle resets and soon enough you will have an algal issue again! Many algaecides even have some nutrients in them which can make algal issues worse in the medium term and can be harmful to fish and water plants if used incorrectly.

So there you have it. Algal issues are multifaceted, but should be treated with a patient, wholistic approach that takes your pond’s particular circumstances into account.

If you have any questions, we solve problems like this every day, so get in touch with us at The Fish Works!



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