"Kirsten Johnsen" wrote in message . net...
I'm new to the group and plants, but during my general research I came
across a site explaining the use of the Redfield ratio to eliminate various
types of algae from the tank.
http://www.xs4all.nl/~buddendo/aquar...dfield_eng.htm

The article states that if you keep a proper ratio of 16:1
(Nitrogen:Phosphorus), little to no algae will be able to survive in the
tank.

Does anyone else in this group have similar findings as the person who wrote
this article?


Hi,

The ratio applies where these are limiting, if there's an ample supply
relative to light/CO2, then the ratio does not matter.

You can have 2 ppm of PO4 and 2 ppm of NO3 as long as this ratio and
levels are stable, it works fine as does 20ppm of NO3 and 0.2ppm of
PO4.

The ratio also includes NH4, which will make a huge difference if a
large fraction of the N is NH4(algae will grow). There are organic
fractions which the plants generally cannot use, a similar situation
occurs with PO4. Algae can use these organic fractions, unlike the
plants. These differences are significant when talking about plants
and algae and dominance in your tank.
Regular large water changes will keep the levels of the organic
fractions down.

In a high light tank you might have to dose more frequently to keep
this ratio but this whole mess with ratios does not limit algae in and
of it's self nor is it that horticulturally important.

As long as the growth needs of the plant are available, then the ratio
can be quite high or low. These are generalized ratios, specific algae
and plants can vary widely.

FW algae have ratios of 14:1 and FW macrophytes have about a 10:1 N:P
ratio.
Redfield's ratio is based on marine algae, not FW macrophytes or FW
algae.

We are trying to grow the macrophytes/plants are we not?
Shouldn't their needs be addressed since that is what we are selecting
to grow? I can also assure you that FW algae can and do grow nicely at
16:1 ratios N:P in many aquariums.

It seems to me if you base this arguement solely on the ratio, 16:1
would favor the algae, not the plants with their richer P content
relative to N.
There's talk about algae's ratio but not the plants which is the focus
of a planted tank.

10:1 ratios are generally mentioned as best for submersed aquatic
plants plants, but this will mainly save you a little KH2PO4 and KNO3
as you do a water changes to prevent any build up or depletion. These
are quite cheap. So as long as all the plants have either, then the
plants grow great and there's little algae presence.

A simple way to maintain a ratio: Do large weekly water changes(50+%)
to prevent any nutrient build up, dose frequently to prevent anything
from running out.

Good plant growth is the key. That is how you outwit algae. That is
the best path IME.

Regards,
Tom Barr