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Allybally Allybally
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  • Posted on: 22/1 7:32
Help please fish dying. Nitrates in tap water? #1
Hi all,

I am new here and looking for some help re water and health of fish. I kept fish years ago in Scotland and had lots of success with Malawian cichlid tank. I am now in East Anglia (considerably harder water) and set up a tropical fish tank in early October for my kids to enjoy. We cycled the tank for 2 weeks. Added 6 male guppies and all was fine until 8 weeks later one fish started nipping the tails of others and one passed away due to stress and 2 passed away with very nipped tails. Water parameters were all fine (using strips - ammonia nitrate nitrite all 0). We went to a different aquatics place who suggested getting some more to keep the bully in check so we purchase 2 female mollies and 4 male guppies (total 2 mollies and 8 guppies in 40L tank). Since then we have lost a fish every couple of weeks and now have only 1 molly and 5 guppies. They tend to become lethargic and have clamped tails with tails hanging down. I added some aquarium salt a couple of weeks ago and have purchased an API freshwater test kit and was surprised to find the tank nitrates are somewhere between 40-80 ppm (ammonia and nitrites 0). I tested the tap water and the nitrates are also 40-80 ppm! Could this be our issue?

Another fish is looking a bit poorly today. His tail is not so fanned out and hanging down slightly (he was the previous bully). I notice the molly has some small white patches on her tail this morning (see photo). Is this fin rot?

Sorry for the long post. Happy to answer any questions and would really appreciate any advice.

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Fishlady Fishlady
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  • Posted on: 22/1 10:22
Re: Help please fish dying. Nitrates in tap water? #2
I'm afraid the shop has given you very poor advice as that is too many fish for a 40L and it's too small for mollies, unfortunately.

Regarding the nitrate reading, the legal limit in the UK is 40ppm, so it won't be higher than that from your tap. You can find out how much is in there by checking the water quality report for your postcode area on your water supplier's website. The level in the tank, however, may be very high as the tank is so overstocked. The API nitrate test is hard to read at/above 40ppm and is very sensitive to being done precisely as per the instructions, particularly shaking bottle #2 very vigorously.

Check your supplier's site and post back the result.
Allybally Allybally
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  • Posted on: 22/1 10:29
Re: Help please fish dying. Nitrates in tap water? #3
Thank you. I did check the suppliers website yesterday and the range of nitrate for this postcode is 16.7-40.7 mg/L.

Any advice what I can do now to help the remaining fish?
Fishlady Fishlady
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  • Posted on: 22/1 10:44
Re: Help please fish dying. Nitrates in tap water? #4
Daily water changes for a while may help - clean water is a great healer. If that doesn't result in an improvement, treat with Esha 20000 as this may be a bacterial infection.
Allybally Allybally
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  • Posted on: 22/1 10:50
Re: Help please fish dying. Nitrates in tap water? #5
Thank you. I have been doing daily 25% water changes for the past few days. I am replenishing the API salt 1tsp/gallon (4L) with each water change. I also use Aqua care tap water conditioner on each change. Do you think it is Ok that the nitrates in the tap water are so high? Do you recommend a product like Tetra nitrate minus to lower the nitrates?

Many thanks.
Fishlady Fishlady
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  • Posted on: 22/1 10:59
Re: Help please fish dying. Nitrates in tap water? #6
Nitrate up to UK limits + 20ppm is OK for typical community fish. I don't recommend treatments like that as they tend to encourage less frequent water changes and that then becomes a problem as regular partial water changes are essential for many reasons other than just reducing nitrate. It also means that when a water change is done, nitrate is added to the tank which is not good - the sudden rise can cause problems of its own. They are an expensive solution to a problem that isn't' really there for most aquariums. When it is important, for sensitive species, the better solution is to remove nitrate from the water before it goes into the tank - either by using RO water (which is what I do, as I also have soft water fish and hard, high nitrate water) or by running a nitrate removing medium such as JBL DeNitrate in the water for a water change the day before it's used.
Allybally Allybally
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  • Posted on: 23/1 7:55
Re: Help please fish dying. Nitrates in tap water? #7
We lost a fish on Thursday and woke up this morning to another one dead. He was a short tail white guppy and seemed fine before bed last night. This morning we have another male guppy swimming around with his tail down. Sometimes he swims fine and he is eating fine but I am worried why he is swimming like this. We have had a few go like this over the past few months and die a few days later.

40L tank
Plenty plants
Ammonia 0
Nitrites 0
Nitrates 40 (tap water is between 20-40)

I usually do a 20% water change each week but the past week I have done 20% each day.

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Fishlady Fishlady
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  • Posted on: 23/1 10:58
Re: Help please fish dying. Nitrates in tap water? #8
I'd be inclined to treat with Esha 2000 or Waterlife Myxazin, suspecting a bacterial infection. Wait 2 days after a water change before treating as the water conditioner can prevent the medication from working. If you have any carbon media in your filter, remove it before treating.
Benjamin Benjamin
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  • Posted on: 23/1 11:14
Re: Help please fish dying. Nitrates in tap water? #9
Re Nitrate.

I had the same problem as you, aquarium level was ~ 80 and tap water , I think ~ 50, also used API liquid tester. The shop recommended Tetra Nitrate tester instead and said that this is the most accurate tester in the market. I have started to use it and my levels dropped to 25 - 50 as the colures are a bit too close for me to distinguish. Also, I have started to dose the water with liquid carbon (on top of the liquid fertilizer) for the plants. As a result the plants started to grow and became healthier effectively consuming ammonia and nitrate from the water column.

I don't know if this will solve your issues but might be something to try.

Best of luck
Allybally Allybally
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  • Posted on: 23/1 14:39
Re: Help please fish dying. Nitrates in tap water? #10
Thank you Fish Lady and Benjamin. I have ordered some more Esha 2000 to put in the tank tomorrow. I will have a look at the Tetra Nitrate test.

Hopefully they pull through 🤞🏻