High Nitrates in my tap water

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Aquarium Advice Apprentice
Jul 14, 2023
I have been keeping fish for 30 years, and probably because they never get diseased or die (apart from normal life span) I have become lazy in testing my water. All of my fish are more than 5 years old. I have a Juwel Vision 180 tank and use the standard in tank filter. I recently did a test of my water and found the following Ammonia 0, Nitrites 0, Nitrates 80 ppm, PH 7.6, GH 16 and KH 5. This high nitrate value concerned me. I then did test on the tap water - Ammonia 0, Nitrites 0, Nitrates 40 ppm, PH 7.6, GH 16 and KH 9. The nitrates in my tap water is quite high and using tap water I am putting in to my tank nitrates at 40 ppm. Unlike the USA where the legal limit for water companies is I believe 10 ppm, the legal limit in the UK is 50 ppm. I only feed my fish 3 times a week.

I have spoken with my local aquatic centre who have suggested getting a RO kit so that I can use RO water and also put in minerals. However this is expensive.

I then went to another aquatic store who did not seem that keen on RO water, and suggested I use RP Nitrate Remover which is a resin you put in your filter.

It would be appreciated for any advice on this matter as to how to reduce my nitrates. I am keen on Seamchem products and use Prime, Stability and Pristine. Does anyone have any experience of Seachem Matrix which could be used in the filter instead of the RP Nitrate Remover.
Do big water changes to drop the nitrates to whatever the tap water is.

Have lots of floating plants in the tank to use the nitrates.

Use the nitrate removing substance or invest in reverse osmosis water if you want to get the nitrates lower.

You can also put tap water in a container and add floating plants. Leave them in the water until the nitrates are 0ppm, then dechlorinate the water (if you have chloramine) and use it for water changes.


You can make a solar still. It would give you pure water, no waste water and be free to make pure water, it just requires a bit of sunlight.

Get a large plastic storage container and put it outside in the sun.
Pour a bucket of water into the storage container.
Put a clean bucket in the middle of the storage container. Have a rock in the bucket to stop it floating around.
Put the lid on the storage container.
Put a rock or small weight on the lid in the middle, so the lid sags above the bucket.

As the sun heats up the container, water will evaporate and condense on the underside of the lid. The water will run towards the centre and drip into the bucket. When the bucket is full of water, you put it into a holding container and put the bucket back in the storage container with another bucket of tap water.

You get pure water with a pH of 7.0, 0 GH, 0KH and no wasted water, no power used and it's cheap to set up.
Thanks Colin_T. That is extremely useful information for which I am grateful
I do know people with " bad water" that set up reservoir systems for holding water and have the water circulating through refugiums where there would be plants or matrix that removes the nitrates then use that water for doing water changes. It all depends on how much space you have and how complex you want to get. Since 40 PPM is the upper limit most like to keep their nitrate levels at, you can also try having the roots of Pothos plants dangle in the tank as these plants do an excellent job of nitrate absorption. If this is not an option, there are a few types of plants for inside the aquarium that are high nitrate absorbers. For example: Amazon frogbit, any of the Duckweeds, Water Wisteria and/or the smaller species of Salvinia. You just have to keep up with plant removal as they will overpopulate an aquarium. (y)
Seachem matrix wont do anything to reduce nitrate. Apart from people who have a financial interest in selling it ive never heard of anyone actually say it reduces nitrate.

It supposedly works by supporting anaerobic bacteria that consumes nitrate and releasing nitrogen gas in a similar manner to how live rock works in marine aquariums. Anaerobic bacteria exists in oxygen deprived environments, so in filter media like matrix or biohome the claim is that anaerobic bacteria can exist deep inside the media after denitrifying bacteria living on the outer surface of the media has consumed all the O2. In reality, water takes the easiest route through the media and will just flow through the gaps between the individual pieces of media. And the pores in the media just get clogged with detritus preventing water flowing through it.

I have more experience with biohome than matrix, but even if we accept it works, the manufacturers recommendations are 1kg of media per 100 litres of water for a moderately stocked tank, and 2kg of media per 100 litres of water for a heavily stocked tank to support anaerobic media. This is a lot of media in big filters. And they also say it takes a year for this anaerobic bacteria to start to grow.

Edit: For clarity. You wouldnt use matrix instead of nitrate remover. Matrix would replace your established biological media. Its fine as biological media to remove ammonia and nitrite, but wont have any effect on nitrate.
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