High Nitrate Effects

Grayling

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My community tank has been a challenge. The tank is a 40 Gallon High and is filtered with a Fluval 206 canister.

It was at one time stocked with 1 - Angelfish, 6 - Neon Tetras, 6 - Zebra Danio, and 2 - Netrite Snails. However about 4 weeks ago, I lost the angelfish, 3 tetras, and 4 danio. I tested the water with an API test kit and the only high reading was the nitrates at around 80 ppm. I've been doing at least 30% water changes each week, but the nitrates remain high. The last test the nitrate level was between 40-80 ppm before a water change and less than 40 ppm after the water change. I tested my tap water which was around 10 ppm. I'm confused. There are 1/2 the fish, but the nitrates remain high in a planted tank. Is this a nitrate level than can cause a rapid die off? I've struggled with fish in this tank for a year now and it's just getting frustrating.

I have a 10 gallon tank with a Betta and have had no issues in this tank.

The only other factor I can think of is a water pH of 7.8, but I don't see how that would cause the fish to die off.


The tank:
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TexasDomer

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What's the temp? This likely isn't the cause for the deaths, but the danios require cooler water (<75 F) and angels require warmer water (>77 F).

Was there anything weird about their behavior before they died? Any sores or wounds?
 
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Grayling

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I have the heater set to 78. The tetras and danios didn't display any odd behaviors, but the angelfish was swimming very disoriented. It'd lay on it's side and swim or spin while it swam. I didn't see any odd spots or sores. I thought maybe an ammonia or nitrite spike was causing the angel's odd swimming behavior, but the test was fine at 0 ppm.
 
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Grayling

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Well I had the LFS test my water just to make sure I was getting the correct readings and they came up the same 80+ ppm. I picked up a new media for my Fulval called clearmax, which is supposed to help with phosphates and nitrates. Right now I guess all I can do is something like 10% water change daily and see if that helps drive down the nitrates before I even think about stocking new fish.
 

junebug

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High nitrates don't mean much... unless the number is over 160 ppm it's likely not an issue (and even then, nitrates aren't toxic, so... yeah).

With such small water changes in your tank over time, the TDS has been building up. This can cause chronic health issues in many fish, so it's possible your fish just kinda "caught" something. How long have you had the tank? Have these fish been in it from the start?
 
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Grayling

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The tank has been setup and running for around a year. The angelfish and neons had been in it for the better of that time. The danios maybe 5 or 6 months.
 

junebug

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One year with only 30% water changes can easily lead to a pretty steep incline in TDS...
 
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Grayling

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Well just finished a big maintenance morning on the tank. 50% water change and a good cleaning of the canister filter just in case it was a culprit in the build up of the nitrate levels. I've made a resolution that I'm going to do a week of daily 50% changes and then back off to weekly 50% water changes. I not going to test for 2 weeks otherwise I might drive myself crazy!
 

TexasDomer

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I don't think you need to do daily 50% changes if your nitrites and ammonia are zero, and you nitrates below 80 ppm. You could do 25% every day or every other day for a week, and then 50% weekly.
 

MtnTiger

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In your position, performing the same amount of WC's, I would be doubting the performance of my filter given your test results.
 
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Grayling

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Well maybe 50% daily is excessive so I could scale it back a little bit. Every other day or smaller daily changes.

How would you test the filter performance? In hindsight, I should have move up one or two models from the 206 but it seems to be doing it's job. The water quality outside of the nitrate levels are being maintained at the proper levels.
 

BDpups

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In your position, performing the same amount of WC's, I would be doubting the performance of my filter given your test results.
What does the filter have to do with nitrates?

And changing 50% of the water daily is fine.
 
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Grayling

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Well my thought was that there was a lot of waste matter in the filter's system and that might help cause elevated nitrate levels. So I cleaned it in some of the water I'd taken out during the WC, but the sponges didn't have a lot of solid matter built up on them and I also put a bag of Fulval clearmax in my top filter tray.
 

TexasDomer

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50% daily is fine, it's just a lot of work to do every day But I do recommend at least 50% weekly in your case (I do between 40-50% weekly too!).
 
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Grayling

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Well I think I'm seeing the effects of just two 50% water changes over the past two days. The remaining fish in their sad little schools are much more active and playful. I'm a little frustrated with myself that I didn't catch the water quality issue sooner. I might have been able to save the angel and some of the tetras and danios. So lesson learned: larger more frequent water changes and more frequent testing especially nitrates when the tank is restocked. I think the issue was TDS as junebug suggested, which I assume is also what I've read about called old tank syndrome. Somewhere in my head a year didn't seem like an old tank, but the math on nitrate build up really tells a bad tale when left undermanaged. Thanks for all the help folks!
 
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