K too low / high

Potassium is an essential mobile plant nutrient and must be supplied by fertilizer. Generally plants take much more of K then they need and store it for later use. Interestingly enough, K is not supplied as NO3 and PO4 by fish waste and plant decay.

FAQ

What happens if there is K deficiency?

Plants keep growing at normal speed but develop holes in leaves especially on older ones.

What is the usual water column K level?

See Plant requirements

What is the lowest K levels I can have with plants?

K levels in fully planted aquariums can drop to zero during a day. If there is daily supply by PPS dosing nothing happens. But uninterrupted zero levels for long period of time may stunt plant growth and recovery can take a long time.

How can I increase K levels?

Increase fertilizer additions.

How much of K fully planted aquarium needs?

Daily about 1.33 ppm. More can be also utilized but in the long run plants will get saturated and will not take more. Not to confuse this with water column K level. This is daily plant uptake compensation.

I have heard about much higher K doses a day, how come?

Some people are pushing plants to grow as fast as possible to increase sales for business and farming.

What happens if there is K excess?

Plants and fish don’t mind relatively high levels.

Can fish die from high levels?

I have not heard of such a problem.

How can I lower K levels?

Check fertilizer. Check water supply for K excess. Check other Plant requirements. Vacuum your substrate. Check filtration system.