Dosing Nitrate

jcook54

Secretary
Staff member
Supporting
Contest Committee
Messages
2,794
Reaction score
3,377
Location
Stone Mountain
I know quite a few folks dose nitrate and phosphate in their systems but I didn't see a lot of first hand accounts here so I thought I'd share my own "whys and hows." I set up a 60g frag tank this summer and it's been coming along nicely. What does one do with a lot of space for frags? Well, fill it up of course! There were standard new tank issues to overcome but it really started getting in a nice groove in early September. Corals were all growing well but their colors stank. I had two obvious issue that I needed to correct - alk swings and low nutrients. I fixed the Alk swings by bringing the doser I had been too lazy to set up online. The nutrient issue was dealt with by doing water changes with "used" water from my main tank. Alk? Check. Nutrients? 5 NO3 & 8 ppb phosphate. The colors started coming back even better than before and I went back to my regular schedule maintenance. A few weeks later I noticed a few corals starting to lose their color again and since I had a few weeks of stable Alk, I tested for nitrates and phosphates and they were barley detectable. I had noticed some macro algae wasn't growing too well a week or two before but didn't connect the dots at the time. I went back to doing water changes with "used" tank water for a few weeks and still couldn't get the levels up. The macro algae started growing again but it sucked NO3/PO4 up so fast that I couldn't ever get detectable levels. So I decided to dose nitrate while I looked for a more permanent solution. (I decided to get additional phosphate by feeding more Full Spectrum pellets)

I did some research and decided to not use the standard stump remover (potassium nitrate) and went with food grade sodium nitrate (NaNO3) instead. It helped that @anit77 had a 5 lb bag that I could "borrow." I dissolved 25g of the NaNO3 is 300mL of RODI water and started dosing! Using a Salifert test kit, I was reading next-to-nothing or less than 0.2 ppm. I added one mL of the solution and waited an hour. I again tested and got a slight increase up to a firm 0.2 ppm. I added an additional 2 mL of the solution and right before I went to bed tested at a solid 0.5 ppm. This is still pretty low and far away from my target of 2 ppm but it's a start. I don't want to do anything too fast and make a headache for myself. Plus, I just left for a work trip this morning and wanted to make sure I didn't screw something up right before I left. For my system it appears that a 2mL dose of the solution raises my nitrates by 0.2 ppm. I don't want to make dosing nitrates a permanent thing but I do want them in a somewhat reasonable range while I work on a more permanent solution. I'll test again later this week when I'm back in town a probably dose a few more times while things get sorted out and I'll keep y'all posted.
 
Oh, I totally meant to include links. There's a decent amount of info about the various methods for dosing nitrates out there and a simple search will show quite a few options.

Here's the calculator I used to make the solutions. Sodium Nitrate is apparently about 20% stronger than Potassium Nitrate so I did the calculation for Potassium Nitrate and multiplied the amount by .84. My goal was a solution using 300mL of RODI water that would raise my nitrates by .25 ppm per mL and I was a little off. Then again, I was testing with a Salifert test and light pink is 0.25 and slightly-more-light-pink is 0.5 so I could be within the margin of error. On point to note, never trust the online calculators blindly. Start slow, test and figure out what's best for your system.

http://www.theplantedtank.co.uk/calculator.htm

Sodium Nitrate (granular)

https://www.amazon.com/Sodium-Nitra...keywords=sodium+nitrate&qid=1578342963&sr=8-5
 
Speaking of nitrates. What test kit do you use?
 
I’m also dosing nitrate and phosphate now, but using Greenleaf Aquarium’s potassium versions of both. I mixed it at 3tsp per liter, which amounts to 0.5ppm per 10mL dose in my 90Gal.

I noticed an almost immediate change in the colors of the SPS. Within 2 days, the colors were more vibrant on everything except my monti cap, which is still a pale pink.

It appears the Xenia and GSP are multiplying faster, as well. That may be coincidental with timing.
 
Salifert. It's not the best but it gets the job done. Especially considering that right now my goal is "around 2" for nitrates. At this point I'd be happy with anything, stable, between 2-5 ppm. I feel like I can confidently get in that range with a Salifert kit.
 
Are you going to be dosing phosphate too? It seems the conventional wisdom from other sites is that the two need to be in balance to get best effects.

Edit: saw you were adding pellets, but is that as reliable?
 
Why not use calcium nitrate instead?

It’s highly water soluble, supplements calcium & won’t affect salinity.

That’s my choice.
 
Are you going to be dosing phosphate too? It seems the conventional wisdom from other sites is that the two need to be in balance to get best effects.

Edit: saw you were adding pellets, but is that as reliable?

I'm going to find out just how reliable they are or aren't. Hadn't been adding any pellets at all so figured it was worth a shot. And when I did the dose calculation for phosphate (using Seachem's Flourish Phosphate) the amount I needed to add to my system was .65mL. Such a small amount scared me a bit because if I was wrong, I could end up cranking up PO4 really quick. May look into it again but wanted to get some nitrates in the system before I got out of town.

Why not use calcium nitrate instead?

It’s highly water soluble, supplements calcium & won’t affect salinity.

That’s my choice.

3 reasons: 1) When I was looking at my options, there was some concern that calcium nitrate might be bound up with a molecule(?) of ammonia. That was confirmed by Mr. Randy Holmes-Farley and with several other options I took calcium nitrate off the table. 2) My goal is to dose the minimum while I increase my bioload to produce nitrates using a more "natural" method. If I end up dosing a lot more quantity or length of time, I may have to reevaluate based on issues of salinity. 3) @anit77 had 5 lbs. that he wasn't using so the price per gram was pretty cheap. The total cost of trying his out was about 1-2 hours of research and 5 minutes preparing the solution.
 
That 1 part of ammonium is rapidly oxidized via bacteria to nitrate. I‘m not worried about it.

Fish excrete ammonia directly into the tank via their gills all day.
 
That 1 part of ammonium is rapidly oxidized via bacteria to nitrate. I‘m not worried about it.

Fish excrete ammonia directly into the tank via their gills all day.

And that good people it why I really like this Club. I never really thought about it @ichthyoid and you're totally right. If I end up nitrate dosing as a regular part of my frag tank husbandry plan I'll have to take a closer look at all the options. Tell me, do you dose phosphates as well? I was a little gun-shy about it since I only wanted to add 6-7 ppb whereas the I needed to bring the nitrates up quite a bit more. Also, do you think adding pellets as food is a decent way to add phosphate or am I just being lazy?

Here's my problem, when I was home a lot in the Fall, things were pretty good. This low nutrient problem reared it's ugly head again after a few weeks of me being on vacation or on the road for work. I try to limit the needs of my tanks when I'm out of town and my Wife takes care of things. I don't have her feeding as much as I might because I don't want her to have the added hassle. She's a real catch in my book and would help however she can but she's already got to deal with the dogs, chickens, the 2 tanks and 100% of the kid related stuff.
 
That 1 part of ammonium is rapidly oxidized via bacteria to nitrate. I‘m not worried about it.

Fish excrete ammonia directly into the tank via their gills all day.
I hadn't seen info on Calcium Nitrate when I bought the Sodium Nitrate. Up until I tore my system down I hadn't wanted to dose something I was so actively trying to remove. All my tanks other than the QT's were all tied to one sump and as such also tied to the ATS. Reduce the photo period and/or intensity of the ATS lights and I had another way to increase the nutrients. I bought the stuff as a backup and never used it. I'll definitely look into Ca(NO3)2 when my frag systems are up and running.

In Justin's case I gave him what I had. He also has a very low bioload in that frag system, three small fish in about 70 gallon of total system volume. So with the bag being free he can experiment with the results. His dosing amount is also very low and it will take quite some time to raise the salinity appreciably. If he get the results he's looking for maybe switching to Ca(NO3)2 would be the better choice for a long term solution. He also has plans to increase the bioload with another fish or two.
 
I'm going to find out just how reliable they are or aren't. Hadn't been adding any pellets at all so figured it was worth a shot. And when I did the dose calculation for phosphate (using Seachem's Flourish Phosphate) the amount I needed to add to my system was .65mL. Such a small amount scared me a bit because if I was wrong, I could end up cranking up PO4 really quick. May look into it again but wanted to get some nitrates in the system before I got out of town.

Makes sense. I'm making my own solution, so I'm able to control the concentration.

I think I got these links from R2R, but I'm blanking on the Google search. These are the products I'm using:

Potassium Nitrate salt:

Mono Potassium Phosphate salt:

1L dispensers:

Mixing with RODI, of course. Used same calculator as you did. It seemed fairly accurate, as my dose is calibrated to 0.5ppm per 10mL of each solution (when added to my ~70 gallons of water). It was very close to the readings I got from my test kits.
 
Fwiw,
I use monopotassium phosphate (also called MPK) on my lawn & buy it in 50 lb bags.

It’s a good water soluble low salt index source of those 2 nutrients.

MPK contains 52% phosphorous, 34% potassium, with the remaining 16% being water. It is hygroscopic (attracts water) so keep it tightly closed.
 
Edited, to read-

Fwiw,
I use monopotassium phosphate (also called MPK) on my lawn & buy it in 50 lb bags.

It’s a good water soluble low salt index source of those 2 nutrients.

MPK contains 52% phosphate, 34% potassium (as K-O), with the remaining 16% being water. It is hygroscopic (attracts water) so keep it tightly closed.

The actual elemental content is 22.7% phosphorous and 28.7% potassium, by weight.
 
Back
Top