Potassium Nitrate

[Kairus]

Decided to try dosing nitrate to lower phosphate since I'm already dosing carbon to lower nitrate. Logic behind it seems sound.

I went out and bought some Spectracide Stump Remover, I took 65mL of it and diluted it into 500mL of RODI water. I used an online calculator which based on a 65g (figure with sand and 100lbs of rock my 72g is only 65g, maybe even 60g) says 133.731g of KNO3 diluted into 500mL will add 2ppm of nitrate with a 3mL dose.

KNO3 has a density of 2.11g/mc3, so 133.731/2.11 is 63.3mL. Does this sound correct?

I dosed 3mL into my tank waited a little bit, tested it with an API kit, and couldn't get a reading, I dosed another 3mL, and nothing. I figure I need to bring it up to about 5-6ppm to get a reading since this kit isn't very sensitive, so I added another 3mL. This was over the course of 3 hours. Still no reading on my API kit. My fish look fine, and my hammer coral is opening up more than usual, which may not be related. Is the nitrate getting used up that quickly, is it the API test, or what?

I want to get a maintenance dose figured out so I can dose it along with my daily dose of vodka (tank, not me!). If I have good results with KNO3, I will order some sodium nitrate so I don't have to worry about potassium levels.

 

[lokii_37]

are you having algea problems? why do you think you need to dose nitrate?

could you dose less carbon and increase nitrate that way?

 

[Michael Hoaster]

So you're trying to lower phosphate, by raising nitrate and carbon levels. Are you trying to optimize C-N-P ratio for plants or macros to outcompete algae for phosphate?

 

[Kairus]

So you're trying to lower phosphate, by raising nitrate and carbon levels. Are you trying to optimize C-N-P ratio for plants or macros to outcompete algae for phosphate?

I'm switching to sodium nitrate, but yes my goal is to balance out C-N-P, but not for macros, for bacteria.

If carbon dosing does work to remove nitrate, and it seems to in my tank, and a lot of other people have had very good success, nitrate could become the limiting factor. We're adding more C, and there's still P in the water so adding more nitrate should help.

I'm curious if it does help or not. I have almost no algae at all in my tank, every 3 days or so a slight film on my glass, but that's it.

 

[Michael Hoaster]

I am very interested in nitrogen dosing, since I am in the planning phase of a seagrass-dominated tank. I've read they could become nitrogen-limited with the required deep sand bed.

So, if I'm hearing you correctly, you're dosing vodka as a carbon source to decrease nitrate, and you're dosing nitrate to decrease phosphate? There must be another benefit to carbon dosing, or else you could just drink the vodka yourself"¦

But you don't have an algae problem. So, is it your goal to get the phosphate to zero, so you never get an algae problem in the first place?

Now THAT'S an advanced topic! If you got really good at this, you'd hardly ever have to change the water! The tricky part would be to adjust for change, but with good test kits and perseverance you could do it.

I look forward to hearing how it goes!

 

[Kairus]

I am very interested in nitrogen dosing, since I am in the planning phase of a seagrass-dominated tank. I've read they could become nitrogen-limited with the required deep sand bed.

So, if I'm hearing you correctly, you're dosing vodka as a carbon source to decrease nitrate, and you're dosing nitrate to decrease phosphate? There must be another benefit to carbon dosing, or else you could just drink the vodka yourself"¦

But you don't have an algae problem. So, is it your goal to get the phosphate to zero, so you never get an algae problem in the first place?

Now THAT'S an advanced topic! If you got really good at this, you'd hardly ever have to change the water! The tricky part would be to adjust for change, but with good test kits and perseverance you could do it.

I look forward to hearing how it goes!

I'm experimenting with a lot of different things, if someone in the hobby has had success with something, and it's provable with low risk, I'll give it a try! If you're interested, here's some of my 'experiments' so far.

I was having algae outbreaks, and cyano outbreaks for the past month but not for these two past weeks. My nitrates have always been zero so I want to see what would happened if I added more nitrate.

The whole premise of carbon dosing whether it's biopellets, vodka, vinegar, etc is to restore the balance between C+N+P in a closed system so more bacteria (and other organisms) can grow. So assuming C is actually limited, if we keep adding C, nitrate is very likely the next thing to be limited because it's consumed so fast by bacteria, algae, diatoms, and coral. So if N is the limiting factor, putting more nitrate in will result in more phosphate being used up. Hopefully then the bacteria is skimmed out.

My phosphates read 0 on Seachem's multitest phosphate, but at one point they were reading 0.5ppm or higher, and I dosed lanthanum chloride into a 5 micron sock for about an hour, tested my water and 0 phosphate, so I felt like I had a clean slate to start on. Since then, I haven't been able to get a reading, so my phosphate levels are being consumed really quickly. I'm sure if I had a hanna tester or something I would get a low reading.

When I switched to heavy actinic lighting I had an explosion of coralline covering rocks that were dry rock a month ago, have no more algae on my rocks, and very little grows on my glass. So I'm not sure if it's just the combination so far, but I'm pretty happy with all the different things I've tried and I plan on testing out soda lime on my skimmer's air feed next.

I wonder if seagrasses use potassium like freshwater plants do? If so, potassium nitrate could be very effective!

 

[Randy Holmes-Farley]

I wonder if seagrasses use potassium like freshwater plants do? If so, potassium nitrate could be very effective!

All growing organisms use some potassium, and all foods contain it. The question is whether there is ever a situation in a reef tank where the consumption outpaces the demand in a significant way. It might, depends on what you grow and what you feed, and whether you do water changes (and how much).

Compared to fresh water, seawater contains a lot of potassium, and the additions from potassium nitrate won't be very much relative to the amount already there.

 

[Michael Hoaster]

Great stuff! It's guys like you who help advance the hobby. I'm very into experimenting as well, but maybe from a more lazy aquarist's perspective!

It's interesting that you're optimizing C-N-P ratios for bacteria and I'm doing the same but for seagrasses.

I'm thinking about using carbon dosing (to increase bacterial biomass) as a means of feeding sponges and other filter feeders, rather than exporting with a protein skimmer, which I'm going to try to do without.

Basically, I want my whole tank to be the filter, working WITH the natural processes that are trying to happen anyway, to achieve my goals. So everything that goes in the tank performs some kind of duty to help keep the tank in balance.