PO4 always low

[wikiboy]

I have a newly setup planted tank (~2 months). What comes to my attention is that PO4 is always low (0 ppm) which causes lots of my plants to have dark green spots. When light is off (8pm), i does 1ppm of po4. To confirm the reading i did a test at 10pm and it reads 1ppm. The next day at 12pm (my light goes on at 1pm to 8 pm), i did a po4 test, and again it reads 0ppm. To verify the problem i did the same routine again but this time i does 2ppm of po4. Next day at 12pm, it reads only at 1ppm.

Is this normal? Does plants consumed po4 during lights off or there are other stuff (like BB) that's consuming the po4?

Can someone advise

[PeterGwee]

Bad test kit......unless you calibrate your test kit and test it against several known standards, you cannot be sure that the test kit is working well. Those spectrometers also needs to be tested against known standards before use in normal lab practices.

I'll not worry about it and dose via EI based on light intensity and do weekly large water changes.

Regards,
Peter Gwee

[wikiboy]

Thanks for the reply. I think i have got the problem rectified. It's due to precipitation with iron as i does them together.

[essabee]

Plants don't live only when lights are on, they are alive the entire 24 hours and follow their life in a routine which is linked to their circadian clock.

Photosynthesis takes place while light is on because the reactions needs the energy garnered from light. Having done all that while the sun was shinning, the plant becomes a storehouse of energy and can use it for other functions of its existence. The portion of assimilation of minerals and other nutrients which are not light dependent, takes place even during no light periods.

Plants don't sleep in the animal sense of the word, though they go through periods of high activity and rest.