Re: excess nutrients

[Thomas Barr <tcbiii at earthlink_net>]

I think folks have gone to the other extreme now:)

You can add too much nutrients and de stabilize a system much like you can
destabilize a system by adding too little.
Destabilization = algae and perhaps plant growth

You are looking for a good middle ground for the plant's needs. While one
single parameter can go very high for awhile, maybe even in the long term,
it's going to give the best results and have least problems by simply
keeping things close to the plant's median needs.

That's why only limiting PO4 very low etc has minimal effects on plant
growth. On some tanks, namely older ones, PO4 maybe be supplied via the
gravel and food that is enough for the plants. Plants don't react as
negatively to PO4 limitation but reduce their NO3 uptake and tissue building
for instance. NO3 limiting reduces many processes and causes color changes
in many plants, holes, yellowing etc. PO4 doesn't cause such obvious
problems.

As far as limiting algae or plants:

If indeed the algae out compete plants for a resource (resource competition)
or vice a versa, then removing the limitation should allow both to grow well
since nothing is holding growth back ........assuming that resource
competition exist.

We do not observe that.
Plants do well when the levels are raised up and algae do not.

So it must be something other than resource competition. The resource in
this case is nutrients. These observations are also seen in nature.

So.......

Some nutrients has a much larger interaction than others.

NH4 for instance really messes everything up(Destabilization) at higher than
normal natural levels. So adding it externally from ammonium sulfate, way
too many fish, agricultural run, septic tank leakage etc will yield a nasty
effect, but normal leaf litter, natural processes tend to add far less NH4
to the systems. 

K+ hardly at all.

PO4/NO3 have a strong effect.

Traces moderate etc.

If you get up to the point where the concentration of some nutrients is so
high that the other nutrients are "bumping into" the needed nutrients, then
you will get interference in nutrient uptake.

But plants are _always_ dealing with this to a certain degree. No soil or
water column is perfect. But as long as extremes are avoided, we have little
cause for concern here. The plants are going to have a work a little to
process their uptake needs no matter what.

It's really simple, like feeding your fish, feed the plants the right
amount, don't starve them, don't over feed them. Don't feed your fish 100%
protein or one food, give them a well balanced diet.

Regards, 
Tom Barr