Potassium Dosing

[labas39]

I did a bunch of research on potassium dosing the last few days and thought I'd share my results.

Using the Salifert Potassium test kit, I've been measuring my potassium, K. It's pretty easy to use and very easy to see the color change. From what I've found, it's rather accurate as well. Currently, my K is at 330 ppm which is rather low. I don't run a ULNS so not exactly sure why it's so low but probably due to the salt mix I'm using.

Anyway, I started to dose using Brightwell's Pottasion-P product. Their page is at:

Brightwell Aquatics Potassion-P

There are discrepancies in their directions so I decided to do some research.

The discrepancies are:

1. Under the Basic instructions, they say add 2 grams, or approx 1/2 teaspoon, of Potassion-P but under the Advanced instructions, they say to add 5 grams, or approx 2 teaspoons. The math doesn't add up. So, I found this PDF that converts weights of common chemical solids to volume:
   
   Mass-Volume Equivalents of Common Chemical Solids
   
   In there, they show that 4.5 grams of potassium chloride, KCl, equals 1 teaspoon. So, the Brightwell's Basic instructions are more correct: 2 grams is approx 1/2 teaspoon. 2 teaspoons is 9 grams, not 5.
   
   (Note that the Brightwell page above states that the ingredients of Potassion-P are potassium chloride (anhydrous) and potassium sulfate (anhydrous). This makes sense since it also states that it's 49% K where KCl has 52.5% potassium.)
   
2. Under the Basic instructions, they say to add 2 grams Potassion-P to 20 gals of tank water but under Advanced, it says to not go over 10 ml of a 5 gram/8 oz. stock solution per 20 gallons of tank water.
   
   They state that 1 gram brings up 1 gallon of water 129 ppm. In the Basic instructions, 2 grams per 20 gallons will raise the K by:
   
   2g * 129ppm/20gal or 12.9 ppm
   
   In the Advanced instructions, the 10ml of stock solution per 20 gallons will only raise the K by:
   
   5gm/8oz = 0.625 grams per oz. of stock solution
   10 ml of stock solution = .34 oz.
   Therefore:
   0.625gm * .34 = 2.1 ppm
   
   At that rate, I'd have to does for eternity to bring the K level up to 400 ppm.

I found a potassium calculator at Ultimate Reefs:

Potassium Supplement Calculator

There, they say not to increase the K per day more than 10 ppm. This is more consistent again with Brightwell's Basic instructions.

I want to start by increasing K by 5 ppm per day. Using the Ultimate Reef calculator, I put 100 US gallons for my Volume, 395 for my Current Level and 400 for my Desired Level, which gives me a recommendation of 4 grams. This again matches up with my hand calculations.

So, I'm going to start with 4 grams of K per day. Since I know how much ATO water I use per day, I've been adding it to my ATO water so that it doses throughout the day.

 

[tgp4274]

hhhmmmm following!!!

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for the commentary!

What salt mix are you using and what salinity? Do you do water changes? Trying to understand how your potassium could get so low. Mine doesn't deplete.

In general, if you know (or believe you know) the amount of any supplement needed, you can often go way above manufacturer directions, which are often for maintenance, not boosting levels.

5 ppm per day is plenty slow enough (assuming the product is pure enough).

From what I've found, it's rather accurate as well.

You mean found what other people said about it, or something you determined?


FWIW, Brightwell has a number of incorrect statements in their various product descriptions, so it doesn't surprise me there might be issues with this one.

 

[phillrodrigo]

Is being 5 ppm low on a 400 ppm recommendation needed. I have researched potassium at all so I'm not saying what your saying is wrong. If my calcium was a consistent 445 instead of 450 I wouldn't worry about it as long as it was always 445.

 

[labas39]

What salt mix are you using and what salinity? Do you do water changes?

I've been using Reef Crystals for many years. I started using it in the past because it stated that they have high K levels. I found a comparison today where these researchers found it to only be at 290 ppm. I found that Kent Marine Reef Salt Mix has many elements in high concentrations; I may change.

I replace about 10% of the water weekly.

As far as the Salifert K test being rather accurate; that was from what other people have said. I don't have a means to test how accurate it really is.

 

[labas39]

I've been using Reef Crystals for many years. I started using it in the past because it stated that they have high K levels. I found a comparison today where these researchers found it to only be at 290 ppm. I found that Kent Marine Reef Salt Mix has many elements in high concentrations; I may change.

I replace about 10% of the water weekly.

As far as the Salifert K test being rather accurate; that was from what other people have said. I don't have a means to test how accurate it really is.

The optimal level of potassium is 400 ppm. My level is at 330 ppm.

 

[TUSI]

Tropic marine pro salt have the highest potassium I believe at around 380 at salinity 0.026. Bright well is not a very concentrated pottasium. Zeovit have a concentrated one

 

[Randy Holmes-Farley Verified Community Expert]

I've been using Reef Crystals for many years. I started using it in the past because it stated that they have high K levels. I found a comparison today where these researchers found it to only be at 290 ppm. I found that Kent Marine Reef Salt Mix has many elements in high concentrations; I may change.

Did you try the kit on your salt mix?

Where did you see that? I'm rather skeptical it is that low. I know the manufacturing specifications for Reef Crystals are a bit above 400 ppm at 35 ppt, and the several tests that I have seen put it much higher than 290 ppm.

FWIW, I use ordinary Instant Ocean, and do not supplement potassium, and I have about 400 ppm potassium, both by kit (Fauna Marin) and by Triton test.

I'd at least consider the possibility that the reading is low for any of these reasons:

1. The test kit measurement is inaccurate.
2. The salinity is low.
3. The tank is using it rapidly for some reason and your foods are not adequately replenishing it.
4. The salt mix was low in potassium.

Only the last two are best solved by supplementation.

That said, if you actually already are near 400 ppm, boosting it slowly to 470 ppm is likely not a big problem.

 

[Randy Holmes-Farley Verified Community Expert]

Is being 5 ppm low on a 400 ppm recommendation needed. I have researched potassium at all so I'm not saying what your saying is wrong. If my calcium was a consistent 445 instead of 450 I wouldn't worry about it as long as it was always 445.

Are you referring to my comment? I wouldn't bother to supplement if my potassium was known to be 395 ppm.

But if it was 325 ppm, I probably would, and there's no need to add potassium more slowly than 5 ppm per day (which was my 5 ppm comment).

 

[phillrodrigo]

No I was just thinking in general. It kind of goes along with the whole chasing numbers thing. I honestly don't have a clue about it it just seems kinda crazy to worry about 5 ppm on 400. 5 dkh on alk would be completely different.

 

[Randy Holmes-Farley Verified Community Expert]

No I was just thinking in general. It kind of goes along with the whole chasing numbers thing. I honestly don't have a clue about it it just seems kinda crazy to worry about 5 ppm on 400. 5 dkh on alk would be completely different.

Yes, that's certainly true. The OP measured 330 ppm, however, which is low enough to think dosing could be worthwhile if that value is correct.

 

[labas39]

Did you try the kit on your salt mix?

I tested my Reef Crystals this morning at the same salinity as my tank, 1.027. It read 330 ppm as well.

For the heck of it, I think I'm going to buy another Salifert kit and compare the values. I bought my current kit a while ago and I want to make sure it hasn't gone bad.

 

[Randy Holmes-Farley Verified Community Expert]

Ok, that sounds like a good plan.

 

[phillrodrigo]

Oops then I'll just mind my business then. I was looking at the part were he put it in the calculator and it said 395 as current number. But jow I get it he does what I do and break it down to see how much you need to go up by 5 ppm. I have a chart which showed how much of each supplement to go up by 1ppm.

 

[labas39]

I bought a new Salifert potassium test kit from my LFS; thanks Reefwise!

I noticed when I got home that there's an expiration date on the box and my old kit expired 7/2014.

This new kit expires 5/2016.

That said, the new kit measured 390!

Yahoo!

Thanks Randy, I could have od'd my tank. I know that acros melt with too much potassium. What that value is I don't know but a local Chicago reefer did it.

 

[Randy Holmes-Farley Verified Community Expert]

You're welcome. Glad to help!

Happy Reefing.

 

[xroads]

If you have a heavy SPS load, the potassium gets used up fairly quickly and will need to be supplemented just like alk, mag, calcium.

 

[Randy Holmes-Farley Verified Community Expert]

If you have a heavy SPS load, the potassium gets used up fairly quickly and will need to be supplemented just like alk, mag, calcium.

FWIW, I don't believe that is true. Many people with heavy SPS tanks do not get depleted potassium.

Unlike calcium, magnesium and alkalinity, potassium is used by all creatures and is present in substantial amounts in all foods. So if a tank is getting depleted, it is because the foods you are feeding and the water you are changing do not contain as much potassium as the creatures growing in your aquarium.

I'm not convinced of the reliability of some potassium kits, but before dosing, I'd get a measurement somehow, either from a kit, or a company such as Triton.

 

[xroads]

Maybe it was the corals I was keeping, I don't know. I sent in samples and found my Pot was 225. After bringing it back up, and dosing regularly to keep it at 400 my SPS really responded positively.

And I did 10% water changes weekly in a 1200G system using Reef Crystals

 

[Randy Holmes-Farley Verified Community Expert]

Maybe it was the corals I was keeping, I don't know. I sent in samples and found my Pot was 225. After bringing it back up, and dosing regularly to keep it at 400 my SPS really responded positively.

And I did 10% water changes weekly in a 1200G system using Reef Crystals

Who tested it? AWT? They seem to get low values, for unknown reasons.

What salinity do you keep the tank at?

Low salinity will always cause low potassium as most salts put in about the amount needed for NSW levels at 35 ppt salinity, while some people keep it a lot lower.