Starting to dose sodium nitrate. How much should I start with?

[cimulation]

I just created a premix of sodium nitrate in order to slowly bump up my nitrates. My tank is 200g of water. 1ml of the mixture should increase my nitrates by 0.1 ppm. I'm currently at 0. How much should my initial dose be?

 

[dwest]

I would go slow at first. I would add 1 ml the first day then test to make sure calculations weren’t way off. After that, raise about 0.5 ppm per day until you get to your desired level, testing frequently along the way.

 

[Randy Holmes-Farley Verified Community Expert]

I'd add 2 ppm a day for a few days and see what happens. Exact dosing is not critical and is easily adjusted as you go forward in time.

 

[arking_mark]

@Randy Holmes-Farley What are the long term effects of adding Sodium Nitrate?

I know the nitrate gets consumed by the tank inhabitants.

However, over time wouldn't the Sodium concentration go up relative to the other ions? And while this may take a long time to become an issue, how does one adjust back?

 

[Randy Holmes-Farley Verified Community Expert]

@Randy Holmes-Farley What are the long term effects of adding Sodium Nitrate?

I know the nitrate gets consumed by the tank inhabitants.

However, over time wouldn't the Sodium concentration go up relative to the other ions? And while this may take a long time to become an issue, how does one adjust back?

It's a great question to ask, but the amount it impacts the already super high sodium in seawater is trivially small (IMO).

Let's compare how the sodium rise when adding 2 ppm of nitrate a day compares to adding 1 dKH a day with sodium carbonate.

First, the nitrate. Sodium nitrate is 27% sodium, so you are adding 0.54 ppm of sodium per day.

Over a year, that boosts sodium by 197 ppm (say, 10,800 ppm to 10,997 ppm)

It will also raise salinity by 0.197 ppt. Assuming you maintain 35 ppt salinity and thus correct for the salinity change back to 35 ppt, the 10,997 drops back to 10,997*(35/35.197) = 10,935 ppm.

So without any water changes, sodium rose from 10,800 to 10,935 in a year of daily dosing. That's a 1.25% rise in sodium.

On the face of it, that is incredibly small, and no reefer or starting salt mix controls salinity and/or sodium to that level. Look at the ICP results for many reefers and sodium varies widely.

Now lets allow 20% water changes monthly. At the end of the 12 months without salinity correction (adding 15 ppm nitrate monthly and doing a 20% change monthly), we are at only 10,868 ppm after a year. With salinity correction, that's only 10,847 ppm (a 0.4% rise in sodium from 10,800 ppm).

OK, let's compare to using sodium carbonate as an alk additive. Each carbonate acts as 2 units of alkalinity, so 1 dKH is 0.36 milliequivalents/L of alk and thus 0.18 milliequivalents of carbonate.

Each carbonate comes with 2 sodium ions, so that is 0.36 milliequivalents/L of sodium. Sodium has a molecular weight of 23 mg/milliequivalent, so one is dosing 0.36 milliequivalents/L x 23 mg/milliequivalent = 8.3 mg/day.

Thus, the rise to sodium is 15 times higher in this case (8.3 mg Na/day) than when dosing 2 ppm nitrate per day (0.54 ppm).

The rise here is also blunted by salinity corrections and water changes, but one might argue it is significant, and it is a reason that it is useful to use a method that supplies other ions (such as potassium) so that they do not get pushed down relative to sodium.

 

[arking_mark]

It's a great question to ask, but the amount it impacts the already super high sodium in seawater is trivially small (IMO).

Let's compare how the sodium rise when adding 2 ppm of nitrate a day compares to adding 1 dKH a day with sodium carbonate.

First, the nitrate. Sodium nitrate is 27% sodium, so you are adding 0.54 ppm of sodium per day.

Over a year, that boosts sodium by 197 ppm (say, 10,800 ppm to 10,997 ppm)

It will also raise salinity by 0.197 ppt. Assuming you maintain 35 ppt salinity and thus correct for the salinity change back to 35 ppt, the 10,997 drops back to 10,997*(35/35.197) = 10,935 ppm.

So without any water changes, sodium rose from 10,800 to 10,935 in a year of daily dosing. That's a 1.25% rise in sodium.

On the face of it, that is incredibly small, and no reefer or starting salt mix controls salinity and/or sodium to that level. Look at the ICP results for many reefers and sodium varies widely.

Now lets allow 20% water changes monthly. At the end of the 12 months without salinity correction (adding 15 ppm nitrate monthly and doing a 20% change monthly), we are at only 10,868 ppm after a year. With salinity correction, that's only 10,847 ppm (a 0.4% rise in sodium from 10,800 ppm).

OK, let's compare to using sodium carbonate as an alk additive. Each carbonate acts as 2 units of alkalinity, so 1 dKH is 0.36 milliequivalents/L of alk and thus 0.18 milliequivalents of carbonate.

Each carbonate comes with 2 sodium ions, so that is 0.36 milliequivalents/L of sodium. Sodium has a molecular weight of 23 mg/milliequivalent, so one is dosing 0.36 milliequivalents/L x 23 mg/milliequivalent = 8.3 mg/day.

Thus, the rise to sodium is 15 times higher in this case (8.3 mg Na/day) than when dosing 2 ppm nitrate per day (0.54 ppm).

The rise here is also blunted by salinity corrections and water changes, but one might argue it is significant, and it is a reason that it is useful to use a method that supplies other ions (such as potassium) so that they do not get pushed down relative to sodium.

Great to know. Thanks!

I've always tried to be ionically balanced with ally dosing.

 

[Randy Holmes-Farley Verified Community Expert]

Great to know. Thanks!

I've always tried to be ionically balanced with ally dosing.

If you can get calcium nitrate, it should be ionically balanced since it ultimately adds alk and calcium in the same ratio as in calcium carbonate. I just don't usually advise it since it is harder to find. But if you can get a quality material, there's no drawback.

 

[arking_mark]

If you can get calcium nitrate, it should be ionically balanced since it ultimately adds alk and calcium in the same ratio as in calcium carbonate. I just don't usually advise it since it is harder to find. But if you can get a quality material, there's no drawback.

I've been trying to use in/out to control nutrients. Not quite there yet...but very close.

 

[Randy Holmes-Farley Verified Community Expert]

I've been trying to use in/out to control nutrients. Not quite there yet...but very close.

That's certainly a fine plan if you can balance the needs to things you feed (fish, etc.) with organisms that are N and P sinks. But it may require a different balance of organisms that many tanks inherently have.