Am I consuming this much potassium?

jccaclimber · Sep 2, 2018

When I started this thread:
https://www.reef2reef.com/threads/suspect-po4-in-the-rocks-and-raising-no3-without-k.421904/
I was concerned about raising my K too high due to KNO3 additions. As of today I've added a bit more than 2 lbf of KNO3 over the last 6 or so months.
I went ahead and got a Salifert test, which is consistently reading around 380, both when I got the test a month ago and today. This isn't that far from my May Triton result of 378 PPM.

If the following calculator: http://www.theplantedtank.co.uk/calculator.htm is to be believed that means I've added around 154 PPM of K in about as many days, and either exported or consumed all of it.

Somewhere between 550 and 600 gallons water volume.
No water changes, although I have removed perhaps 30 gallons in the last several months via skimming, acclimation, etc. I've also exported a LOT of bryopsis (now cured with Fluconazole) and a decent amount of other macro.

I am dosing 2-part (haven't calculated the PPM/day), but unless the algae is consuming it all I'm not sure where it's going. Growth is good (1" monti cap frags to 6"-8" colonies in 6-12 months), but I still feel like my input is really high.

Thoughts?

Randy Holmes-Farley · Sep 2, 2018

There are several sinks. Using a two part that does not include it will drop potassium simply by the salinity effect alone. 128 ppm per year when dosing 1.1 dKH per day is about the expected value, assuming no water changes.

Also, every living thing that is growing consumes it, but all foods that are organisms tissues contain it. Rinsing foods, however, may wash some away, especially from frozen foods, so the net effect might be a decline over time (but not always).

jccaclimber · Sep 2, 2018

Randy, I understand how adding a potassium free 2-part will deplete all other elements if water changes are being done, but without water changes I don't understand how 2-part addition on its own would result in potassium depletion, which puts me back to consumption or other means of export.

I'm not rinsing my food, although there's not a lot of food going in at the moment either (nori and KNO3, and some phyto being the main additions as I wait for the phosphate to lower).

If I understand you correctly the tank really is consuming that, which leads me to believe that I will need to supplement K in addition to my KNO3, particularly if I stop using KNO3. Off in freshwater land I've dosed K2SO4 before. Is this one of those things like boosting Mg. where a combination of K2SO4 and KCl is appropriate? Do you have a recommended ratio?

Edit: Is there a recommended maximum concentration of potassium increase per day, or can I do it all at once?

Randy Holmes-Farley · Sep 2, 2018

A two part raises salinity. When you correct the salinity back to normal ( whether you know you do it, or it happens via skimming etc, it has the effect I mentioned. That effect requires no consumption at all. That’s how the figure I quoted was determined.

I’d raise potassium slowly.