Is high nitrate ok for established planted tank

[TwoTankAmin]

Too much info and potentially confusing. Llet me try to simplify it if I can.

Let's start with one quick fact. Ammonia (NH3) is a gas. When it dissolves in water it turns mostly into Ammonium (NH4). Some would say that NH3 is 100 times more toxic to fish than NH4. That is an exaggeration but still true. Most of our ammonia test kits measure Total Ammonia which is the sum of NH3 and NH4. The level at which NH# starts harming fish id 0.05 ppm.


Plants do not make nitrate, but they can use it. They prefer ammonia in the form of ammonium (NH4). A very few species actually do prefer nitrate. When plants use ammonia, they do not make nitrite (NO2) or nitrate (NO3). When plants use nitrate they convert it back to nitrite and then to ammonia, As a result this process is much less efficient.

The bacteria prefer ammonia (NH3). this is the toxic form. When the bacteria use ammonia they make nitrite and then they make nitrate.

The plants need nitrogen as do the bacteria. They do have some choices in how they get it. Most of the bacteria can also use ammonium (NH4) but not as efficiently as the NH3. But plants can also die from elevated ammonia (NH3).

Therefore, the more plants you have the less bacteria you will have and the less nitrate you will have. In a high tech heavily planted tank people may even add nitrate back in because some beileve the plants need a bit. I used to add potassium nitrate to mine.

Therefore if you are getting nitrate readings in a planted tank over about 20 ppm, then you do not have enough plants or the right type of plants to process more of the ammonia. the bacteria are doing more of the work. This is not a bad thing as long as you change water weekly. Also, a well planted tank depletes some things, but not all things from the water.For this reason it is as important to do weekily water changes in planted as well as unplanted tanks. You are trying to get everything back into the needed balance.

 

[StevenF]

When researching cyanobacteria I found that some plants can use Nitrates but it uses a lot more energy. From what I remember not all plants have this pathway to get nitrogen. 35ppm of nitrate seems really high, where do you get your water?

In a high tech heavily planted tank people may even add nitrate back in because some beileve the plants need a bit. I used to add potassium nitrate to mine.

N2 gas is the only form of nitrogen that plants cannot use. They get their nitrogen from ammonia, urea, amino acids from decaying organic materials. It is easy for plants to use these forms of nitrogen. They also can use nitrate but it takes several processing steps for plants to use it so nitrates are absorbed more slowly.

In high tech planted tanks (CO2 and high light you can aacually see nitrate levels drop with a nitrate test. And when ammonia, nitrite, and nitrate levels go to zero plant growth does slow or stop.Farmers also apply nitrate fertilizers to their fields. Since nitrate is less toxic than nitrite and ammonia Nitrate is the preferred fertilizer. Some people however have used synthetic urea CO(NH2)2.but there is no test to detect its it is impossible to monitor the levels of it. I have used nitrate in and urea in my tank and my tank does go through frequently go through 10ppm of nitrate in about a week.

To get plants to grow fast enough to absorgbe a noticeable amount of nitrate it is important that you have all 14 of the nutrients plants need.n From my own experience if you are short of nitrogen phosphates from fish waist tends to build up. I you are short on one nutrient other than nitrogen, nitrate may build up as bacteria consume fish wast.

 

[momsspaghett]

When researching cyanobacteria I found that some plants can use Nitrates but it uses a lot more energy. From what I remember not all plants have this pathway to get nitrogen. 35ppm of nitrate seems really high, where do you get your water?

I got RO water from my fish store down the road when I did a 80% water change. My tap is about .25-.5 ammonia and 5 nitrate as is.

 

[momsspaghett]

Too much info and potentially confusing. Llet me try to simplify it if I can.

Let's start with one quick fact. Ammonia (NH3) is a gas. When it dissolves in water it turns mostly into Ammonium (NH4). Some would say that NH3 is 100 times more toxic to fish than NH4. That is an exaggeration but still true. Most of our ammonia test kits measure Total Ammonia which is the sum of NH3 and NH4. The level at which NH# starts harming fish id 0.05 ppm.


Plants do not make nitrate, but they can use it. They prefer ammonia in the form of ammonium (NH4). A very few species actually do prefer nitrate. When plants use ammonia, they do not make nitrite (NO2) or nitrate (NO3). When plants use nitrate they convert it back to nitrite and then to ammonia, As a result this process is much less efficient.

The bacteria prefer ammonia (NH3). this is the toxic form. When the bacteria use ammonia they make nitrite and then they make nitrate.

The plants need nitrogen as do the bacteria. They do have some choices in how they get it. Most of the bacteria can also use ammonium (NH4) but not as efficiently as the NH3. But plants can also die from elevated ammonia (NH3).

Therefore, the more plants you have the less bacteria you will have and the less nitrate you will have. In a high tech heavily planted tank people may even add nitrate back in because some beileve the plants need a bit. I used to add potassium nitrate to mine.

Therefore if you are getting nitrate readings in a planted tank over about 20 ppm, then you do not have enough plants or the right type of plants to process more of the ammonia. the bacteria are doing more of the work. This is not a bad thing as long as you change water weekly. Also, a well planted tank depletes some things, but not all things from the water.For this reason it is as important to do weekily water changes in planted as well as unplanted tanks. You are trying to get everything back into the needed balance.

Thank you for the information! Since I filled the majority of the tank with RO water and cleaned out the sponges, I’m sure now the tank will be able to adjust and fix itself to get that balance. Do you leave your nitrates at 0?

 

[momsspaghett]

My tap water is 35ppm nitrate but my tank is usually 0-10ppm depending on how recently I have performed a water change, so it seems my plants are soaking it up. It could be that there is some anaerobic activity in the filter too.
Whenever I set up a new tank nitrate remains high until the plants become established and I have found that high nitrates actually seem to stunt the plants. My solution has been to chemically remove the nitrate for a week or two until they start growing after which I can stop. So for me, plants definitely don't seem to like high nitrates much above 20-30ppm.

How do you chemically remove nitrate?

 

[raylove]

How do you chemically remove nitrate?

I used JBL NitratEx resin. 24hrs in your filter will substantially reduce nitrate levels. You don't leave it in or use it permanently and you recharge the resin by soaking in salt water. I have found two cycles are enough to get my plants growing, after which they can deal with the increased nitrate levels that result following water changes with tap water that is high in nitrate.

 

[AbbeysDad]

Although you'll especially find for example on the planted tank forum many that will recommend high(er) nitrates for the planted tank. (as mentioned) Great for plants, not so much for fish and inverts. I believe (as others have mentioned) that lower nitrates of 20ppm (or less) is MUCH better for the long term health and well being for aquarium inhabitants.
Check out my article on Lowering Aquarium Nitrates and for a deep dive check out Filtration and Water Quality