Article on Nitrate Uptake of Terrestrial and Aquatic Plants


Lifetime Charter Member
Lifetime Member
Jul 27, 2007
New Hope, Pennsylvania
Thought this was interesting at the end of page 6 to see the nitrate uptake of Hornwort.

"In an experiment in which the initial nitrate concentration was 350 ppm, it reduced the concentration to 75 ppm in nine days, corresponding to a half-life of 4-5 days. It removed on average about 2 ppm per day per gram of plant..."

Tom Barr

Staff member
Jan 23, 2005
I mentioned about a 10 or so years ago, we found about 1-4ppm per day of uptake in a planted tank. Many at the time vigorously questioned this range.
Some still do.
Mark from Monterey Bay Aquarium measured some surge uptakes of 8ppm per day of NO3 in some of their tanks.

Per gram of plant, wet weight vs dry weight also makes a huge difference when comparing these rates.

Per gram of plant biomass is the fair comparison, some folks/hobbyists like to suggest that their tanks are all are on equal terms when it comes to plant biomass(they discuss their tank as a whole, not as a function of per gram weights), when clearly, even a novice can see that, they are not.

Still, most folks will do this, but species, the scape design(open layout vs dense jungle etc) and biomass really can and do vary greatly.

That's the way I used in my research and in the latest installment of the BarrReport to use for comparisons.

I've not seen any aquarists, and few companies other than SeaChem, and Tropica do this.

So this begs the question: what are they really comparing(myself included) when they state such rates?

They should compare more and report a range, rather than 1.5 ppm per day etc.
If all you have is one system and are not willing to deviate much in the routine , then it's really hard for you to compare to other systems.

Many of us on the APD were very wary of this years ago, today, few even consider it on the forums.

Do not believe everything you think.

Tom Barr


Junior Poster
Aug 3, 2007
Baltimore, MD
Tom, you mentioned in earlier post that the max nitrate uptake is 1-4ppm. Why not just dose daily 5ppm and save some ferts? Just wonderin'?

Tom Barr

Staff member
Jan 23, 2005
Or dose 10ppm 3x a week? :D

3ppm per day ought to do it.
Also, fish loading is a large player here.

Plants can take up that much, it can(does mean that they will in all cases) make them grow faster.

But is faster growth your goal?
Is non limiting growth a goal?

For some, yes. In order to rule other limitations, you need to provide non limiting levels to investigate things individually.

For others, they are not interested in that, they also tend not to be good at isolating cause and effect as well:rolleyes:

Limiting growth for horticultural reasons, say you want slower growth, then limiting light is the 1st option since we have control of that. That makes everything much easier.
Then comes CO2.
Then Nitrogen(NH4 and/or NO3)
Or perhaps PO4.

Tom Barr