# Is potassium oxide(K2O) safe to use?



## Lomond (Jan 1, 2006)

Hi,

My local gardening store sells Sulphate of Potash as potassium oxide(K2O). Can I use it for Potassium in my tank?

The label gives an analysis which also states: soluble in water: 48.0%,
and it also says 39.9% K.

Kind Regards,

Andy


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## jude_uc (Feb 7, 2006)

Sulphate of Potash is K2SO4, the stuff that greg watson sells. My understanding (from the seachem folks) is that they have to list it in terms of K2O because it's required by law for standardization. If "sulphate of potash" is all that i'm the mix, I would assume it's safe to use.

-Adam


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## Lomond (Jan 1, 2006)

Thanks for your reply Adam,

I also saw that Seachem mention K2O but describe it as Potassium _Sulfate_ rather than potassium _oxide_. Are these the same thing? I hope so because it is dirt cheap from gardening stores!

Andy


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## jude_uc (Feb 7, 2006)

Neither seachem potassium nor sulphate of potash is potassium oxide. It just turns out that potassium oxide (just plain potash, not sulphate of potash) used to be the standard for fertilizers. Because of that, the law requires that regardless of the source of potassium in a fertilizer, you express it in terms of the equivalent amount of potassium oxide. The whole system, including the names 'potash' and 'sulphate of potash' are very archaic, by hey, that's life.

-Adam


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## titan97 (Feb 14, 2005)

I've been using muriate of potash from my local nursery store. It, too is listed as K2O, but I know that is it KCl. I'm not real happy about adding Cl to my tank, but it was cheap ($3 for 5 pounds). It has been working great. The only other downside besides the Cl is that is has a bunch of red stuff that won't dissolve. It doesn't seem to effect the aquarium, but I was a little afraid at first. I'd say "full speed ahead" with the sulphate of potash.

-Dustin


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## HeyPK (Jan 23, 2004)

I got the same muriate of potash. I am sure that the red stuff that doesn't dissolve is iron oxide, used as a filler. I just let it settle out and draw off the clear solution. Actually, the red stuff might make a nice iron supplement for the substrate!


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