PO4 too low / high

Phosphorus is an essential mobile plant nutrient and needs to be supplied by fertilizer or fish waste. Generally plants take much more of PO4 than they need and store it for later use. Interestingly, plants can take up daily supply of PO4 in 30 minutes.

FAQ

What happens if there is PO4 deficiency?

Plants start growing slowly and become weaker and vulnerable to algae infestation.

What is the usual water column PO4 level?

See Plant requirements

What is the lowest PO4 levels I can have with plants?

PO4 levels in fully planted aquariums can drop to zero during a day. If there is daily supply from fish waste or PPS dosing nothing happens. But uninterrupted zero levels for long period of time may stunt plant growth and recovery can take a long time. It is better to keep PO4 levels in the recommended levels.

How can I increase PO4 levels?

Feed your fish more and dose more fertilizer. Some situations may require doubling the PPS-Pro fertilizer. PPS-Classic adjusts itself automatically to any conditions.

How much of PO4 fully planted aquarium needs?

Daily about 0.1 ppm plus fish waste. 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 PO4 level. This is daily plant uptake compensation.

I have heard about much higher PO4 doses a day, how come?

Some people are pushing plants to grow as fast as possible to increase sales for business and farming. Some found plants to be more resistant to algae in certain conditions.

What happens if there is PO4 excess?

Plants don’t mind relatively high levels but fish do. For fish high PO4 levels are toxic.

Can fish die from high levels?

Not immediately. It takes weeks or months of getting weaker and wasting away.

How can I lower PO4 levels?

Check fertilizer. Check water supply for PO4 excess. Check other Plant requirements. Vacuum your substrate. Check filtration system. Consider lower ratio of fish load to plant mass.