Check my K dosing math (or should I use the whole bottle?)

[SteveM]

OK, first I know, gregwatson.com is the answer. But on a whim while ordering some other stuff, I got a bottle of Kent Botanica K. I didn't really look at the details - it was on sale so I added it to the cart. Now that I have it I am looking at dosing, and wondering if my numbers are correct. Ok, actually I'm pretty sure my numbers are correct, but since I can't test K I figured I'd put this out there:

Bottle claims 40,000 mg/L K. Recommended dose is 1ml/10G once a week. By my math that is a whopping 1ppm K. Right?

Now I have read lots of suggestions as to the recommended dosage of K, and they pretty much start at 20ppm and run up to 100ppm. Right?

So for my 75G to dose 20ppm K I use 150ml? This bottle isn't going to last long - I guess $5 isn't too expensive for a lesson learned

 

[malkore]

No reason to exceed 20ppm of K in any planted tank. Some people only maintain 10ppm and have beautiful plants. Since I don't waste time measuring K, I err on the side of caution and dose 15ppm after a water change (with remaining K coming from KNO3 dosing).

However it sounds about right. I know I used a $7 bottle of SeaChem Potassium in 3 weeks on my 75gallon, and doubt I ever had enough in there to clear even 10ppm.

On the plus side, you'll have a spare bottle for mixing up gregwatson.com ferts. I recommend KNO3, K2SO4 and Plantex CSM+Boron. If you have high light/CO2 injection, you'll need some phosphate too. You should only make dosing solutions for phosphate and PLantex. KNO3 and K2SO4 get used more, so it's a lot easier to dry dose each time than make a bottle of dosing solution every other week.

 

[jsoong]

Your calculations are right, Steve.

I had the same experience, bought a bottle of supplements without reading the fine prints & finding that the 500 ml bottle only lasts me 3 water changes ..... so I switched to KNO3 powder instead.