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Keeping fish pond water clean, clear and healthy

Maintaining good water in fish ponds

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

Ponds are full of life and we aim to encourage the pond to be biodiverse in order to maintain a healthy balance.

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 some algae in the pond as this is a natural part of the ecosystem.

As much as we do try to emulate a natural environment, fish ponds come under pressures that are generally not seen in nature.

Firstly, we tend to stock fish ponds with often 100s of times more fish weight per volume of pond that we would find in nature, so then we have to feed all of this increased biomass and then have to deal with the waste that these fish produce, all while expecting our water quality to be like that of a swimming pool.

Therefore, we need appropriately sized biological pond filters that will help us to remove all of the waste produced by the fish and process the nutrients that would otherwise accumulate in the pond and make our fish sick and our water quality diminish.

ou can learn more about biological filtration here

It is important to not put too many fish into your pond.

As a rule, we like to have a maximum of 4 or 5 koi per 1000 litres of water. Not exceeding this number of large fish in a water body will help ensure that your water will stay good and in the event of a power outage or pump failure, your fish are less likely to suffer from lack of oxygenation in the water.

Less fish obviously means less food, so your filtration system will be able to deal with the fish waste more effectively. We like to feed our fish whatever they will totally consume in a minute or two. You can read more about appropriate feeding quantities here

Even in ponds with the correct amount of fish, filtration and the right amount of feeding can still have water quality issues.

Different ponds have differing levels of sunlight, temperature swings, plant cover, fish stocking levels, feeding regimes, filtration systems, volume, water depth, etc.

When we trying to improve the quality of the water, it's important to try to get to the root causes and treat them, rather than just treat the symptoms

Although the causes of poor pond water quality may be multidimensional, the symptoms often manifest in one or more of the following ways.

Brown muddy water

This could indicate that your fish are digging into water plants or that your filtration is not adequate / not being cleaned often enough. First, try to eliminate the source of the dirt and then try to remove the dirt itself by backwashing your filter more often.  Flocculants can help with this process by binding suspended particles, either sinking them or making it easier for them to get caught in the pond filtration system.  You can buy flocculants here

“Tea stained” water

indicates that there are rotting sticks/leaves in the pond. Net out leaves more regularly and do more frequent backwashing of the filter.  The addition of activated carbon to areas of water movement can assist in removing trace amounts of tannins and you can see them here

Algae issues

Green water or excessive string algae. As mentioned earlier, a bit of algae in the pond is natural. But sometimes it can be a bit much!

If the water is going green, then your filtration is either not adequate or the UV light bulb needs changing! UV lights will kill single-celled algae. 

Buy replacement UV globes here

String algae tends to occur in the spring and summer months when the good bacteria levels are low. Early spring is a great time to add beneficial bacteria weekly.

For more information regarding algal issues, please read this article

In general, water quality issues can be multidimensional, so we need to compile a complete picture of all the factors that contribute to our little pond ecosystem. The first step is to do a water test.

Test for pH, ammonia, phosphates and nitrates and let us know the results. We have test kits available here if you need one.

We recommend doing monthly water tests (or additional tests if you think something is not quite right!) We also provide a free water testing service at our shop if you do not have a test kit.

Just bring a water sample up in a clean jar and we can test it for you. We can have a chat about any of the other factors that might be affecting your water quality and make recommendations so that things can improve.