Nitrates and small fish

[Scaperoot]

   I've read conflicting information on this, so I'm wondering, how do you gauge whether nitrates in a tank are too high? I'll use one of my tanks as an example. It's a 20 long heavily planted tank with White clouds, Guppies, false Juliis, a female betta, nerites, and cherry shrimp. If I'm using a master test kit, what's the threshold before I need to do a water change? I try not to over feed, but I've noticed lately that I'm getting higher readings. At last water change, Nitrates were 80+. The frequency was typically 7-10 days between water changes, but I've had to do them weekly for about a month now. I feed 6 days a week; frozen baby brine, pellets, freeze dried ACO food, and occasionally some crushed Krill flakes. 

[Biotope Biologist]

The answer to that question is rather complicated because there are many variables involved that contribute to nitrate poisoning.

 

I will be succinct here and say as a general rule for long term health of the fish you want to keep it under 30 ppm.

[Mmiller2001]

There’s no reason to go over 30ppm, even in a heavily planted CO2 tank. So I would change water when you reach 30 and if you have plants, keep it between 20 and 30.

[Galabar]

You may consider feeding less.  The input to your tank (food) ultimately ends up as nitrate (less what is absorbed by plants).

Are you fertilizing the plants (and with what)?

[BeeD]

I start changing at first registration of nitrates because in the past I've noticed that once the buildup starts, I usually don't have a good enough log of events to predict how fast the climb will be. I had one tank evolve over the course of years without cracking 0. I went without testing it for a month (or 2 maybe), tested and it was at 20ppm. I thought back and realized a few things.

The biggest miss... I wasn't noticing deceased adult ramshorn snails, because the plant carpet was thick. There had been a snail population explosion after my gourami - a savage fry and larva hunter - passed. Many of those adult snails must have died within a short period of time. The plants probably picked up the ammonia spikes, because they prefer ammonia to nitrate, so I assume that compounded the nitrate buildup. 

[Scaperoot]

On 12/14/2023 at 10:56 PM, Galabar said:

You may consider feeding less.  The input to your tank (food) ultimately ends up as nitrate (less what is absorbed by plants).

Are you fertilizing the plants (and with what)?

I dose easy green weekly. 

[Galabar]

On 12/15/2023 at 11:46 AM, Scaperoot said:

I dose easy green weekly. 

Easy green will be a source of nitrate.

[Scaperoot]

On 12/15/2023 at 1:11 PM, BeeD said:

I start changing at first registration of nitrates because in the past I've noticed that once the buildup starts, I usually don't have a good enough log of events to predict how fast the climb will be. I had one tank evolve over the course of years without cracking 0. I went without testing it for a month (or 2 maybe), tested and it was at 20ppm. I thought back and realized a few things.

The biggest miss... I wasn't noticing deceased adult ramshorn snails, because the plant carpet was thick. There had been a snail population explosion after my gourami - a savage fry and larva hunter - passed. Many of those adult snails must have died within a short period of time. The plants probably picked up the ammonia spikes, because they prefer ammonia to nitrate, so I assume that compounded the nitrate buildup. 

We lost two mystery snails in this tank a couple weeks ago, but I removed them the same day. We may have lost Nerites or some fish and not noticed. I'll have to check in hard to reach areas. 

[Angiemike6]

Which test kit are you using to test the nitrates.  The API one is very difficult to judge what the nitrate level is, and from my experience also tends to give a much higher reading than say the NT Labs kit.   I have a 40 gallon community tank where Ammonia is 0, Nitrits are 0, PH is 7.8, GH is 17 and KH 6.  My nitrates are between 40-80 using the API test.  As the other readings are fine, and my fish are not dying or getting stressed I have stopped worrying about the nitrate level, which in the water supplied by my water company is 32 ppm in any case.   I also only feed 3 times a week, as waste food can contribute towards high nitrates.

[Scaperoot]

On 12/24/2023 at 2:19 PM, Angiemike6 said:

Which test kit are you using to test the nitrates.  The API one is very difficult to judge what the nitrate level is, and from my experience also tends to give a much higher reading than say the NT Labs kit.   I have a 40 gallon community tank where Ammonia is 0, Nitrits are 0, PH is 7.8, GH is 17 and KH 6.  My nitrates are between 40-80 using the API test.  As the other readings are fine, and my fish are not dying or getting stressed I have stopped worrying about the nitrate level, which in the water supplied by my water company is 32 ppm in any case.   I also only feed 3 times a week, as waste food can contribute towards high nitrates.

     I use the API liquid test kit. I don't know what to think anymore. Some people swear by the ACO strips, others go by API. I just do a water change if I see dark orange to red results. I stopped using the strips. 

[Tanked]

On 12/14/2023 at 9:33 AM, Scaperoot said:

   I've read conflicting information on this, so I'm wondering, how do you gauge whether nitrates in a tank are too high? I'll use one of my tanks as an example. It's a 20 long heavily planted tank with White clouds, Guppies, false Juliis, a female betta, nerites, and cherry shrimp. If I'm using a master test kit, what's the threshold before I need to do a water change? I try not to over feed, but I've noticed lately that I'm getting higher readings. At last water change, Nitrates were 80+. The frequency was typically 7-10 days between water changes, but I've had to do them weekly for about a month now. I feed 6 days a week; frozen baby brine, pellets, freeze dried ACO food, and occasionally some crushed Krill flakes. 

No matter which test kit you use, nitrates <50 ppm are considered safe but not ideal.  Test strips are not intended to be precise.  They are intended to be fast and easy guide for everyone to use, for a lot less money.  Their biggest draw back is that the ammonia test requires purchasing a different strip.  The API tests can be more precise, but are also more prone to operator error.  I've always been curious about how they determined that the Master Kit does 800 tests.

As to how to get the nitrates closer to to 30ppm, you could test your tap water for nitrates, feed less, and do more but smaller water changes.