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The Goldfish Gazette, Issue #044 -- Green Pond Water
August 31, 2017

Goldfish Care Tips and Guidelines

A Free Monthly Resource For Goldfish Enthusiasts
August 2017
Issue #044

In This Issue
Green Pond Water

There is nothing more annoying than spending valuable time cleaning out a pond only to find in starting to turn green within days.

Green Pond Water

With smaller ponds say up to 200 gallons, having to make frequent water changes because the water has turned green isn’t too much of a problem, but a 1000 gallon pond can be a major undertaking.

The most common reason ponds are cleaned out is because the water has turned green from an algal bloom.


The simple solution you would think is, install a filter.

A filter is recommended for all goldfish aquariums and ponds because of the amount of waste the fish produce. The problem is a filter won’t filter out algae (unless it is a special filter such as a diatom filter).

The primary purpose of a filter is not to clean the water, but to process waste into harmless compounds. These harmless compounds (nitrates) are plant food, so essentially filters are plant food producing factories. Add some sunlight and the two elements required for plant life have been provided, food and sunlight.

Natural Solutions

Natural solutions include frequent water changes, reducing light levels, very low fish numbers, water plants or a combination of all four.

Frequent water changes are the best solution, but during summer when algae blooms are at their worst, there can be restrictions placed on water use by local water authorities.

Light levels have to be very low. I use shade cloth rated at 50% shade, and the ponds are partially shaded by trees, but my water still turns green.

Water plants compete with the algae for food and can also create shade. Problems with plants are they usually need periodic pruning to keep them in check and many die back in winter. Plants are a natural food for Goldfish so only the hardiest varieties such as vallisneria and lilies can be used.

Even with very low fish numbers, pond water still turns green in strong sunlight.

Having a natural balance of low fish numbers, sufficient sunlight to maintain thriving water plants and sufficient rainfall to refresh the water is hard to achieve, especially across all four seasons, so in most cases an artificial solution is the answer.

UV clarifiers

UV clarifiers are very effective and will keep the water spotless.

They are best run in conjunction with a filter otherwise the clarifier's rudimentary filter will quickly clog.

Stand-alone clarifiers can be run as needed. The only disadvantages with them are the UV lamp needs to be replaced yearly and they need a power supply.

Some larger filters have UV clarifiers fitted which saves extra plumbing and power leads.

Chemical Solutions

I have found commercial pond products to be effective in aquariums but less effective in ponds. Some readers may have had better success. Drop me a line and I can pass this information on to others.

I’ve made a recent discovery of a new product on the market manufactured by an Australian company called Splosht International Pty Ltd. I’ve included it under chemical solutions but it is a natural product containing several types of beneficial bacterial.

Water is treated by simply adding an initial 15g dissolvable sachet of powder into the pond followed by a 2.5g sachet every two weeks.

Between four and six weeks later the water is claimed to become crystal clear. I am currently running tests and had hoped to report on the results in this e-Zine but my water has been just above 10oC which is the lowest temperature the bacteria will be effective.

The product directions do state that colder water will slow the clearing process down. I will report on the results next month as the test will have been running for 9 weeks.

Whatever method you use to keep your pond water clear, keep testing your water to make sure the pH, nitrates and ammonia levels are all as they should be. Unless your pond receives a lot of rainfall constantly, you will still need to make regular water changes.

To read more on Splosht click here…

Comments? Ideas? Feedback? I'd love to hear from you. Just reply to this e-zine and tell me what you think, or what topics you want covered.

Next Month's Topic

Emergency First Aid

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