High PO4 a problem in low-tech planted aquarium with no CO2 enrichment?

[evanluke]

I work at a local fish store that specializes in planted aquariums. Often times we are tempted to recommend phosphate based buffers to help people manage pH on aquariums that are cycled with a few hardy fish and a small amount of plants.

This usually results in tanks with very high PO4 numbers. My question is, in the absence of any type of CO2 supplementation, will very high PO4 numbers (5ppm+) make plants more difficult to grow?

I know we don't worry about high PO4 numbers in EI tanks with CO2 injection or even low-tech EI tanks with excel supplementation, but what about tanks with a definite CO2 limitation?

 

[Biollante]

Difference I Suspect Between Salt & Organics

Hi,

I have not seen a problem with PO4 to around 7 or 8-ppm. Haven't seen a problem above that, but I haven't looked either.

Biollante

 

[Tom Barr]

In non CO2 planted tanks, much like wetlands, the soil/water is limited by N, not P(like CA).
In some systems, the reverse might be true(Everglades, FL).

Regards.,
Tom Barr

 

[evanluke]

Thanks for your responses. I know I've seen a post from Tom somewhere (maybe theplantedtank?) which details how the PO4 algae myth came about.

It was something to the effect of high PO4 exacerbating a CO2 deficiency as PO4 tends to drive CO2 uptake in plants.

Can you give me a scenario where high PO4 can contribute to an algae problem?