Potassium Depletion and Two Part Usage

Randy Holmes-Farley · Sep 26, 2015

I'm curious to collect some info from those people who see potassium depletion in their aquaria. I've never really been convinced that potassium should deplete based on coral usage, and yet it is the people with a lot of hard corals that seem to see it and dose it.

Now it occurs to me that people using a two part that does not have enough potassium in it may see depletion simply due to the increase in salinity from the two part, which, when lowered back to normal salinity, will effectively look like potassium depletion.

In fact, someone who doses the equivalent of 4 dKH of alkalinity per day using a two part with no potassium will, over the course of a year, drop potassium quite a lot. Assuming you readjust salinity every day, it drops from 400 ppm to 237 ppm. Half that amount of two part will drop potassium by half as much, to 319 ppm. And finally, someone adding only 0.37 dKH per day will drop potassium from 400 ppm to 367 ppm.

This all assumes no water changes and imports from foods and such exactly matching consumption (which it might roughly do, depending on the system).

So to the poll. I cannot know whether commercial two parts add sufficient potassium, but I suspect that DIY two parts that do not use the Dowflake I originally tested (which has adequate potassium in it) may be adding too little potassium in some cases if they are now using more purified calcium chloride materials.

What have you observed?

hatfielj · Sep 26, 2015

Randy, I dose Red Sea products (their color line A, B, C, and D) to help keep up with my potassium and other trace elements. K was very low in the past. I haven't rechecked it since starting dosing, but my corals have been doing great. In fact, before I started dosing it I had some unexplained STN that stopped immediately once I started dosing these and feeding more. So, I was already under the assumption that two part alone was not enough to keep up with coral health (apparently I wasn't doing enough water changes to keep up with the trace elements?)
I have a question though...
I was wondering if it would be possible to add those Red Sea supplements to my 2 part solution(s) so I don't have to do it manually everyday?

Here is a link to the red sea products I'm talking about:http://www.redseafish.com/coral-coloration-program/coral-colors-abcd-supplement-pack/

Randy Holmes-Farley · Sep 26, 2015

hatfielj said:
Randy, I dose Red Sea products (their color line A, B, C, and D) to help keep up with my potassium and other trace elements. K was very low in the past. I haven't rechecked it since starting dosing, but my corals have been doing great. In fact, before I started dosing it I had some unexplained STN that stopped immediately once I started dosing these and feeding more. So, I was already under the assumption that two part alone was not enough to keep up with coral health (apparently I wasn't doing enough water changes to keep up with the trace elements?)
I have a question though...
I was wondering if it would be possible to add those Red Sea supplements to my 2 part solution(s) so I don't have to do it manually everyday?

Here is a link to the red sea products I'm talking about:http://www.redseafish.com/coral-coloration-program/coral-colors-abcd-supplement-pack/

What two part are you using? Red Sea's?

It's hard to say what can be mixed without knowing exactly what's in them (and their description is rather odd, for example listing F2 in part A, which almost definitely is not in it in that form), but I think you may be able to:

1. Mix A into either part, but I'd start with the alkalinity part.
2. Mix B into either part
3. C may not go well with either part, but I'd try the calcium part first.
4. I really can't say what is in D, and I probably would not mix it.

Bear in mind there's a reason they did not put all these together (well, probably there is), so adding more than one into a single part of a two part might itself lead to combination issues.

If you see any cloudiness form, that combination didn't work out.

hatfielj · Sep 26, 2015

I use Bulk Reef Supply's two part. I guess I can take a little sample of both 2 part solutions and try mixing them together with each to see if they precipitate. Thanks for the advice!

Randy Holmes-Farley · Sep 26, 2015

hatfielj said:
I use Bulk Reef Supply's two part. I guess I can take a little sample of both 2 part solutions and try mixing them together with each to see if they precipitate. Thanks for the advice!

You're welcome.

Did you vote in the above poll? If so, you voted the wrong category. BRS is a DIY.

Russ265 · Sep 26, 2015

my results may be skewed. i dose potassium nitrate and usually gain 10ppm a month.

i use seachem reef carbonate and reef code a

Randy Holmes-Farley · Sep 26, 2015

Russ265 said:
my results may be skewed. i dose potassium nitrate and usually gain 10ppm a month.

Meaning every month is gets 10 ppm higher? Isn't that a road to a problem of excessive potassium?

Russ265 · Sep 26, 2015

Randy Holmes-Farley said:
Meaning every month is gets 10 ppm higher? Isn't that a road to a problem of excessive potassium?

excessive in terms of?
to answer your question though. a 20% wc of regular io drops it about 30-40ppm.

hatfielj · Sep 26, 2015

Randy Holmes-Farley said:
You're welcome.

Did you vote in the above poll? If so, you voted the wrong category. BRS is a DIY.

Oops, yes I voted wrong then!

Randy Holmes-Farley · Sep 26, 2015

Russ265 said:
excessive in terms of?
to answer your question though. a 20% wc of regular io drops it about 30-40ppm.

I'm confused. IO at 35 ppt has about 400 ppm of potassium, and a 20% change that dropped 400 ppm to 360 ppm would mean that the salt you are using would have only 200 ppm potassium in it.

biom · Sep 26, 2015

I'm using DIY two part, analytical grade chemicals, Alk consumption 1.5 dKh, i'm trying to keep K close to 390 ppm. potassium depletion is about 1 ppm per day (Salifert test), 20% wc weekly (390 ppm K freshly mixed). That's why I added about 0.5 grams KCl per every 10 grams CaCl2.2H2O in the calcium part to compensate potassium depletion.

Randy, can you calculate please how much KCl i should add to my Ca/MgCl2 mix (Real Two part

) to compensate K ion displacement. And i'll report back in a month or so after, if there is still K depletion. I believe there will be because im dosing carbon and probably part of potassium is exported by skimmer together with bacteria. You know some strains of bacteria are capable to accumulate potassium 1000x more than concentration in surrounding water.

And to add - I've used calcium reactor and there were potassium depletion, but I was under full Zeo (zeolites, carbon dosing, etc.).

Russ265 · Sep 26, 2015

Randy Holmes-Farley said:
I'm confused. IO at 35 ppt has about 400 ppm of potassium, and a 20% change that dropped 400 ppm to 360 ppm would mean that the salt you are using would have only 200 ppm potassium in it.

except... i usually do a 20% wc at 500ppm
i have 480 ppm right now.

io has potassium around 360-400 (its a mixed bag) ime, rc 420. i could be off by the amount of the wc. but generally that is what i see

Randy Holmes-Farley · Sep 26, 2015

Russ265 said:
except... i usually do a 20% wc at 500ppm
i have 480 ppm right now.

io has potassium around 360-400 (its a mixed bag) ime, rc 420. i could be off by the amount of the wc. but generally that is what i see

Why so high?

Randy Holmes-Farley · Sep 26, 2015

biom said:
I'm using DIY two part, analytical grade chemicals, Alk consumption 1.5 dKh, i'm trying to keep K close to 390 ppm. potassium depletion is about 1 ppm per day (Salifert test), 20% wc weekly (390 ppm K freshly mixed). That's why I added about 0.5 grams KCl per every 10 grams CaCl2.2H2O in the calcium part to compensate potassium depletion.

Randy, can you calculate please how much KCl i should add to my Ca/MgCl2 mix (Real Two part ) to compensate K ion displacement. And i'll report back in a month or so after, if there is still K depletion. I believe there will be because im dosing carbon and probably part of potassium is exported by skimmer together with bacteria. You know some strains of bacteria are capable to accumulate potassium 1000x more than concentration in surrounding water.

And to add - I've used calcium reactor and there were potassium depletion, but I was under full Zeo (zeolites, carbon dosing, etc.).

Sure. I was planning to do that for an upcoming article anyway. I can't right now, however.

Russ265 · Sep 26, 2015

Randy Holmes-Farley said:
Why so high?

accumulated nitrate dosings and lack of water changes. i havent seen any detriment.
i just drop it when it gets to 500 or close to it.

a fresh batch of reef crystals gives 420ppm.

if i am inadvertantly stressing corals because of it, i havent noticed.

Cory · Sep 27, 2015

Ive noticed potassium deplete a lot in my old tank with chaeto growing. I had to supplement potassium. I dont think the corals used it as much as the chaeto did. Iirc it dropped 20ppm or more per week.

mbsun · Sep 27, 2015

I use balling classic, and have around 1.2 mg/l loss of potassium per day, and have experienced this for around 2 and a half years.

I dose nitrate, however there is no dissernable differance to potassium depletion

I am fairly inconsistent regarding harvesting of macro algae from the sump. Again no differance

I dose around 1.5 dkh worth of bicarb into a heavily sps set up, some big montipora, a lot of which have been replaced by acropora recently (mak8ng me doubt the montipora/potassium anecdote)
Withdrawal for salinity is around 0.1% per day of system volume, so clearly potassium depletion is well in excess of withdrawal even if the sodium free salt did not contain potassium- which it does

I keep potassium now at 430-440 to give me margin for error.

I also do not water change, though i had the same potassium use both before and after stopping wc

Still baffles me as to where it all goes

ifarmer · Sep 27, 2015

i use brightwell part a and part b but never test for potassium.

Chameleon · Sep 28, 2015

I've never tested potassium but rely on two part from bulk reef supply in addition to kalwasser. I do do semi regular water changes and occasionally drop in a few mLs of a potassium nitrate solution I made up a long time ago and forgot the concentration. that was mainly to supplement some nitrates though.

Righteous · Oct 1, 2015

Using Bionic 2 part at 10ml per day in 14 gallons of system water. Been dosing for at least 12 months. 15% water change a week. Triton test from last month showed potassium at 420ppm.