Nitrates in tap water - tropical tank

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Nov 6, 2018
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Hello all

I've kept tropical fish for a few years now, and it has been a fairly casual hobby but recently I've decided that it was high time I learnt more about it and so I will be the first to admit I don't know as much as I should. Please be gentle...

I have a Fluval 180l tank which came with a Fluval 207 canister filter, and I've been religious about maintaining it, changing the filter media, and so on. I hoover the gravel each time I clean, and the tank performance has generally been excellent, except for the nitrates. Given how well everything else was working, I was puzzled how high the nitrates were (80-120ppm), and it suddenly occurred to me to check the tap water. Why I hadn't checked earlier, I don't know - anyway...

The nitrates in my test sample were 80ppm straight from the tap - in fact it seems that on some water changes when I test prior to changing the water, the tank/filter has actually managed to reduce the level from the tap water! Of course I go and spoil this by adding tap water to the tank.

So the question is - what can I do about this? I'm not in a position to get and store large quantities of purified water (I've read about buying reverse osmosis water - not sure if that's viable for me given logistics and storage space). Is there an additive I can put in tap water for example to bring down the nitrates? I'm currently treating it with API Stress Coat which I've had great results from, especially in stress reduction. That claims to treat most aspects of tap water, but not nitrates.

Equally, I'm aware Fluval (and others) make filter substrates that can reduce nitrate presence - for example peat, which appeals because my tap water is around pH 8.0 and I think from doing a bit of reading my tank inhabitants would benefit from a slightly lower pH.

So - thoughts please? If it's, "you must absolutely get reverse osmosis water" then I'll find a way. Equally I am very much open to other suggestions.

Side note - I live in South East England - tap water here is very hard - not sure if that makes any difference?

Thanks in advance!
Hi there are a few things you can do you can get filters you can run water through when doing a water change or you could add ro water when you do a water change.

I would get in touch with your water company though as the legal limit in the uk is 50ppm so 80ppm might be a sign you have a problem with your drinking water.

Thanks to both - I'll certainly investigate the water quality angle - will do some more testing to make sure it's a consistent issue. In the meantime I've ordered a water filter from an aquarium supplier that claims to remote nitrates - reviews look pretty favourable so I'll see how that goes!
Hi @sparkyjf. I use a pozzani aquarium nitrate removal filter. It removes all the nitrates from my tap water. You can connect it straight to your kitchen tap using a garden hose pipe. You may need to to buy an adapter for your tap ( depending on what tap you have ). I got one from Wilko for about £1. It’s very easy and doesn’t require plumbing in.

The down side is that the filters need replacing quite often. My tap water is about 20ppm nitrate straight from the tap, and I need to change the pozzani filter about once a month / every 6 weeks. ... That’s doing a 40% water change once a week in a 125liter. I have lot of live plants which help as well.

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