Why would nitrate remain near 0 ? - The Planted Tank Forum
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post #1 of 35 (permalink) Old 12-25-2019, 11:49 PM Thread Starter
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Why would nitrate remain near 0 ?

I have a 20L with 17 pygmy, 4 juvi angels, 1 clown pleco, 3 otto and 2 1/2 guppies (the 1/2 is a 2? month old fry the angels missed). The tank has been setup for approx 10 weeks. The filtration are two sponge filters (one in each corner) and approx 6 weeks ago i added a nano 30 out of paranoia. I cannot figure out why the nitrate are staying below 5. There are plants in the tank but there are plants in all my tanks. I've done two 50% water changes on this tank in 10 weeks it has been setup (the last one was 1 week ago). Could the sponge filters have nitrate eating bacteria ? I would expect the nitrate to be around 20 or 30 with the minimal water changes and fish load. The other tanks have reasonable nitrate levels (i measure several tanks at a time - i have 4) and this is the only tank that remains well below 5. The plants are not dying but i would not say they are growing esp fast (the crypt in the back shows some growth and the anubia in front put out a new leaf last week but the dwarf grass is just sitting there not dying but not growing/spreading).
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I'm concern because something doesn't make sense (all my tests are performed with api liquid test). I feed the angels 3 times a day since they are juvi - the seem healthy though they bicker some - they have been in the tank about 8 weeks - my guess is that they are 3 or 4 months old - i'll move them when they get a bit larger - right now they seem to have plenty of room - when the bickering gets too harsh the small one goes left corner and the next smaller one goes to the right corner.
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Oh the tank has 40lb (approx 2 1/2 - 3 inches) of moonshine substrate (so total water height is not that great).
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post #2 of 35 (permalink) Old 12-26-2019, 12:54 AM
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I'm guessing the 20L is a typo?

I'd usually say you might not be shaking the bottle enough on your test kit, but if you are getting readings on the others then that's probably not it - although retesting and giving it a really good shake before starting wouldn't hurt.

The plants maybe using nitrate but could be short of something else - are you fertilising? That may help the plant growth.

Looks like some of your plants are reaching the surface - they'll grow and use nitrate (or often the ammonia before it can be converted to nitrate) better when they break the surface as they can use CO2 from the air.
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post #3 of 35 (permalink) Old 12-26-2019, 07:28 AM
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Could also be with sugar sand your using the lower layers of sand have gone anaerobic and are now functioning as a denitrifying filter.
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post #4 of 35 (permalink) Old 12-26-2019, 08:59 AM Thread Starter
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Fyi: 20L is not a typo - it is a 20 long. I'm not sure I understand what you mean by sugar sand? Would anaerobic gravel be bad ?

I was getting some cyano algae so i started adding some fertilizer the past two weeks. This picture was taken before i added the fertilizer - there is a little cyano in the picture on the left middle front and not shown in this picture a blob grew on the heater (pretty thick). It was easy to pull off as a single sheet and at that point i added fertilizer and did the water change. It also coated one plant leaves but that also pealed off pretty easy - took about 2 minutes and didn't stick at all.
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I have this gravel in one other tank but black algae is growing on the substrate in that tank (that tank gets regular water changes - about 50% once a week and has a lower fish population (3 angles, 6 white fin rosy tetra, 4 kuhli and a sae) it is a 29. The nitrate in the 29 runs around 15 - hence the weekly water changes. Not sure why black algae grows in that tank (not on the plants just on the gravel).
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post #5 of 35 (permalink) Old 12-26-2019, 12:12 PM
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Doubt you have enough anaerobic bacteria to break down nitrates if your stocking is as you say it is.

20 litre ranks are nano tanks. Unless your tank is very very thin and long I think that it is more likely that your tank is a 20 gallon. Could you send in measurements?
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post #6 of 35 (permalink) Old 12-26-2019, 01:57 PM Thread Starter
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20 Long is a standard american size tank - it is 20 gallon (nearly 76 liter). 20 Long is pretty small for angels; i'm not sure i would even try one angel in a 20 liter - sorry for not being clear the first time.

The dimension is 30 long; 12 high 12 wide (inches)

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Originally Posted by Jordan_Deus View Post
Doubt you have enough anaerobic bacteria to break down nitrates if your stocking is as you say it is.

20 litre ranks are nano tanks. Unless your tank is very very thin and long I think that it is more likely that your tank is a 20 gallon. Could you send in measurements?
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post #7 of 35 (permalink) Old 12-26-2019, 04:56 PM
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I might throw in a couple thoughts. One is that having "some" nitrate is likely to be okay as the plants are not doing without. But then if one wants to find a cause, it sometimes helps to get a different view of the tests. I find API nitrate extremely hard to get the right answers and that prompted me to go for the slightly higher priced Salifert test for my nitrate. My thinking is that there is little reason to test if the test doesn't give the right answer, so that allows me to go with the little bit of extra expense to really get an answer that I can trust. Seems to be a problem with my extremely hard water but perhaps, worth a try to see how a different test looks at all your tanks. Different color using pink makes it better for me.
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post #8 of 35 (permalink) Old 12-26-2019, 05:25 PM
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My guess is that your test result is false. API test kit requires vigorous shaking of Test Liquid 2 to get accurate result. Try to shake Liquid 2 100 times before dispensing to see if you get different results. Over time, Liquid 2 will expire before the content is used up due to changing concentration, so even vigorous shaking won’t guarantee good results. I have abandoned API and switched to Salifert Nitrate Kit which uses powder in lieu of Liquid 2. With no need for shaking, Salifert results are consistently more accurate than API.
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post #9 of 35 (permalink) Old 12-26-2019, 05:57 PM
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What fertilizer are you adding how much nitrogen does it have? Some fertilizers have very little nitrogen and if you have reasonable plant growth nitrogen levels would drop close to zero. are you using this fertilizer in your other tanks? How does the size of the tanks and stocking compare.I honestly don't think you have enough fish in the tank to make much nitrate.
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post #10 of 35 (permalink) Old 12-26-2019, 08:19 PM
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I wouldn't worry too much about the nitrate. When I set up my heavily planted 40 breeder it took months to register any nitrate at all despite the fact that it was fairly heavily stocked. I just assumed that the plants were sucking it all up.

As for the fish it seems you already know that you can't keep the angels in a 20 long for any length of time. I wouldn't even keep one in a tank that size. And I would definitely not keep angels with pygmy Corydoras either. My keyhole cichlids ate some of mine and they are smaller than adult angels.


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post #11 of 35 (permalink) Old 12-26-2019, 09:08 PM
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Quote:
Originally Posted by jake21 View Post
Fyi: 20L is not a typo - it is a 20 long. I'm not sure I understand what you mean by sugar sand? Would anaerobic gravel be bad ?

I was getting some cyano algae so i started adding some fertilizer the past two weeks. This picture was taken before i added the fertilizer - there is a little cyano in the picture on the left middle front and not shown in this picture a blob grew on the heater (pretty thick). It was easy to pull off as a single sheet and at that point i added fertilizer and did the water change. It also coated one plant leaves but that also pealed off pretty easy - took about 2 minutes and didn't stick at all.
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I have this gravel in one other tank but black algae is growing on the substrate in that tank (that tank gets regular water changes - about 50% once a week and has a lower fish population (3 angles, 6 white fin rosy tetra, 4 kuhli and a sae) it is a 29. The nitrate in the 29 runs around 15 - hence the weekly water changes. Not sure why black algae grows in that tank (not on the plants just on the gravel).
Sugar sand is sand with really small grain size about like processed sugar you by at store, average grain size of sand is .3-.75mm, which is what I’m seeing in picture.

Being that small the pore structure in between grains are is very tight and oxygenated water has a very hard time reaching lower layers. When oxygen is low a different type of bacteria will form, anaerobic bacteria. They actually strip nitrates of their oxygen molecule to breath and turn nitrates into nitrogen gas which drifts back up through gravel into water, up to surface and dissipates into atmosphere.

The light blue/green algae forming on surface of sand around tank also supports that this is happening in your sand. They are a nitrogen fixing Cyanobacteria that uses the nitrogen gas being released from sand to grow.

And anaerobic bacteria has nothing to do with stocking levels as one poster alluded to. Only thing required to grow anaerobic bacteria is any presence of nitrates in water column and low oxygen levels.

All anaerobic bacteria activity is not bad, in fact it’s a important part of the nitrogen cycle in nature. Only in the presence of high levels of raw organics can it become lethal to your tank, you will not have that problem as your sand layer is so tightly pored almost all raw organic matter stays at surface where it is broken down by aerobic bacteria to nitrates. Anaerobic activity is exactly how Seachem Matrix and other nitrate reducing media like biohome etc work. You can actually build a denitrification filter if you want, people have been building them for decades.
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post #12 of 35 (permalink) Old 12-26-2019, 10:57 PM Thread Starter
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Hum... as i said i test my tanks in parallel - so that if the test is false for one it should be false for all but the tanks get expected readings that have been cross-checked at the lfs.

Quote:
Originally Posted by Tiger15 View Post
My guess is that your test result is false. API test kit requires vigorous shaking of Test Liquid 2 to get accurate result. Try to shake Liquid 2 100 times before dispensing to see if you get different results. Over time, Liquid 2 will expire before the content is used up due to changing concentration, so even vigorous shaking won’t guarantee good results. I have abandoned API and switched to Salifert Nitrate Kit which uses powder in lieu of Liquid 2. With no need for shaking, Salifert results are consistently more accurate than API.
That is possible i guess - this substrate is extremely fine grain (too fine grain for my taste). The difference between this tank and the other tank i have with this gravel is that this tank has the substrate on the glass bottom. The other tank has ugf plates and a corner cut out around the mittenberg filter to get a tiny bit of flow through it (it is not hooked up to an air-tube) in that tank i get a lot of black algae on the substrate but no Cyanobacteria; that tank nitrate runs around 15 (it has a light bio-load - 3 angels; 6 white fin rosy tetra and 4 kuhli).
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This makes it sound i shouldn't be too concern that the nitrate level is staying ultra low and it won't harm the plants or fish.

Thanks

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Originally Posted by DaveKS View Post
Sugar sand is sand with really small grain size about like processed sugar you by at store, average grain size of sand is .3-.75mm, which is what I’m seeing in picture.

Being that small the pore structure in between grains are is very tight and oxygenated water has a very hard time reaching lower layers. When oxygen is low a different type of bacteria will form, anaerobic bacteria. They actually strip nitrates of their oxygen molecule to breath and turn nitrates into nitrogen gas which drifts back up through gravel into water, up to surface and dissipates into atmosphere.

The light blue/green algae forming on surface of sand around tank also supports that this is happening in your sand. They are a nitrogen fixing Cyanobacteria that uses the nitrogen gas being released from sand to grow.

And anaerobic bacteria has nothing to do with stocking levels as one poster alluded to. Only thing required to grow anaerobic bacteria is any presence of nitrates in water column and low oxygen levels.

All anaerobic bacteria activity is not bad, in fact it’s a important part of the nitrogen cycle in nature. Only in the presence of high levels of raw organics can it become lethal to your tank, you will not have that problem as your sand layer is so tightly pored almost all raw organic matter stays at surface where it is broken down by aerobic bacteria to nitrates. Anaerobic activity is exactly how Seachem Matrix and other nitrate reducing media like biohome etc work. You can actually build a denitrification filter if you want, people have been building them for decades.
Yea - the angels will be removed long before they can eat the cories. The plan is to move the blacks in the 29 to the 120 when they pair off (they are probably around 6 months old); and then move the platinum to the 29 (I think they are currently 4 months old - so move them when they are around 6); when the platinum pair i'll either put the other two in the 120 or give them to the lfs and then keep the pair in the 29. Not optimal but should be ok if they are mostly by themselves.

Quote:
Originally Posted by Triport View Post
I wouldn't worry too much about the nitrate. When I set up my heavily planted 40 breeder it took months to register any nitrate at all despite the fact that it was fairly heavily stocked. I just assumed that the plants were sucking it all up.

As for the fish it seems you already know that you can't keep the angels in a 20 long for any length of time. I wouldn't even keep one in a tank that size. And I would definitely not keep angels with pygmy Corydoras either. My keyhole cichlids ate some of mine and they are smaller than adult angels.

Last edited by jake21; 12-27-2019 at 12:11 AM. Reason: more details
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post #13 of 35 (permalink) Old 12-26-2019, 11:11 PM Thread Starter
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I'm using thrive C. I just started it last week (12 days ago) in this tank. I use it in the 120. I have 1 120g; 2 29g and 1 20 long. The 120 runs around 30 nitrate; the two 29 run around 15 nitrate. I do regular water changes on those three tanks - and i use fertilizer about once a month (and root tabs once every 3 months). Plant wise one of the 29 is doing fantastic; the other one is a mix bag - the center piece plants were aponogeton ulvaceus and i think they went into hibernation. They dropped all their leaves but the bulbs are not soft - the problem is there are so many hybrids out there i'm not sure if i should leave the bulbs in the tank; take them out and store them in water or store them in a dry place (all three options seem to depend on the specific hybrid you picked up).
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One of the 29 look fantastic but the other one has developed black algae on the substrate (it doesn't grow on the plants just the substrate - which is the same fine white sand in the 20 Long; the other 29 has a slightly coarser black substrate from stoney river (estes). The 120 has eco-complete black - which is too coarse for my taste. Grain size wise the stony river seems to work best for my purpose - though if the fine sand stuff is really keeping hte nitrate near 0 that is something to consider.

Quote:
Originally Posted by Surf View Post
What fertilizer are you adding how much nitrogen does it have? Some fertilizers have very little nitrogen and if you have reasonable plant growth nitrogen levels would drop close to zero. are you using this fertilizer in your other tanks? How does the size of the tanks and stocking compare.I honestly don't think you have enough fish in the tank to make much nitrate.
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post #14 of 35 (permalink) Old 12-27-2019, 10:18 AM
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Is that spraybar at right end blowing straight down?

Also if you look at pic on left end of that tank, where sand is not as thick as other areas of tank you’ll notice there is absence of blue /green algae on top of sand. Unless this is area that you recently vacuumed the lack of algae there also supports the anaerobic theory.

But yes in a low tech tank like this you can very easily dose a fert that has nitrates and phosphates like Reg Thrive every other day and not worry about it.

I myself would rather adjust/modify circulation patterns in tank and make that anaerobic activity go away. It’s really not that hard to do.

If you want good knowledge on substrate pore size and processes that happen at Microbial layers in substrate read Dennis Wong’s page on substrate and next page on microb/layerining, it is 100% dead on accurate, actual, factual science.

https://www.advancedplantedtank.com/...substrate.html

Your tank has the good anaerobic type of bacterial activity, only down side to it is that tank will constantly be nitrate and phosphate limited.
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post #15 of 35 (permalink) Old 12-27-2019, 02:05 PM Thread Starter
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That is the intake to the filter - the spray bar is horizontal on the right side. I'll read the article you linked. Is there an easy way to control the blue/green stuff without making changes ? Mostly I don't want it coating the plants leaves but it would be nice if it didn't coat the gravel (either). I don't mind the anaerobic activity as long as it doesn't harm the fish but and i presume it is a positive to eat up all the nitrate (as long as the plants get enough) but if there is a trivial way to control the rate i might try that.
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I wonder why the other tank ends up with black algae instead of this green jello - maybe there is just enough flow in the ugf plates to kill the bacteria ?

Quote:
Originally Posted by DaveKS View Post
Is that spraybar at right end blowing straight down?

Also if you look at pic on left end of that tank, where sand is not as thick as other areas of tank you’ll notice there is absence of blue /green algae on top of sand. Unless this is area that you recently vacuumed the lack of algae there also supports the anaerobic theory.

But yes in a low tech tank like this you can very easily dose a fert that has nitrates and phosphates like Reg Thrive every other day and not worry about it.

I myself would rather adjust/modify circulation patterns in tank and make that anaerobic activity go away. It’s really not that hard to do.

If you want good knowledge on substrate pore size and processes that happen at Microbial layers in substrate read Dennis Wong’s page on substrate and next page on microb/layerining, it is 100% dead on accurate, actual, factual science.

https://www.advancedplantedtank.com/...substrate.html

Your tank has the good anaerobic type of bacterial activity, only down side to it is that tank will constantly be nitrate and phosphate limited.
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