What organics can I make a tea with K in it?

I used worm casing tea using molasses and my plants thrive in it.
I think I’ll use bat g for P but for K,I’m not sure what to use for K so after I bubble it’ll turn alive and become readily availible like worm casings and bat g.
Any suggestions?

There are many fish farms in my area,fresh spring water fed ponds and they are loaded with P and K.They have N it it but there is a special breed of fish to keep green growth down to prevent too much N.
What is strange EC is 0 even though it has great levels of P and K in it.Can that happen?