Re: Of Phosphates and Nitrates

On Fri, 25 Oct 1996, Calvin Chin wrote:

> 1. Nitrates and phosphates usually go hand in hand inducing heavy algal
> growth. Supposing we manage to get rid of phosphates in the aquarium but
> Nitrates are still present. Will Nitrates alone be sufficient for algae to
> grow? Which is a better nutrient for algal growth? Is it Phosphate, or
> Nitrate, or are both needed?

This is an easy experiment to do.  Fill a bare tank with
phosphate-free tap water, add PMDD, and see what grows.  Fungus will
(I've found it in pure PMDD), but I don't think any algae will survive
without P.

> 3. Supposing the regime as prescribed by Paul and Kevin works, does it mean
> that I can do away with the bi-weekly water changes and just change water
> only when phosphates go out of control?

Nonononono!  P isn't the only thing that builds up in an aquarium.
All sorts of organics and unused trace elements will accumulate over
time.  You may need to do fewer water changes, but you'll never
eliminate them completely.  I change 25% every 1-2 weeks.

> 4. Will this regime be actually superior to the traditional regime as
> prescribed by Dupla? (i.e. no nitrates in the fertilliser at all!) I do
> understand that this regime is a lot cheaper compared to sticking to Dupla's.

Anyone care to run some side-by-side tests?

> 5. Instead of adding Nitrates, will it be just sufficient to increase the
> feeding of my fish (relying on the extra Nitrates produced.) But I also
> understand that phosphates will no doubt, increase. Does anyone know the
> proportion of increase in Nitrates as compared to Phosphates in an aquarium?
> (e.g. will Nitrates increase twice as much as Phosphates, etc.)

No idea what the ratio is.  There certainly isn't nearly enough K, as
I've routinely been able to reduce [NO3-] to unmeasurable levels by
adding K2SO4.  Increasing your feeding as a means of fertilizing your
plants isn't a good idea for several reasons - bacteria will bloom,
organics will build up, and your fish will get fat (can't have that, now
can we?).  Not to mention that, at most pet stores, fish food is roughly
7 billion times more expensive than agricultural chemicals for an equal
number of moles of a given nutrient.

> I do hope that the scope of the Phophate-Nitrate debate could be widened
> through these few points and folks with experience could share them with the
> rest of us :), because Paul and Kevin's theory will really revolutionise
> things if it is indeed true (read no more water changes?).

I'll say it again - don't skimp on the water changes!
Kevin Conlin  Montreal, Canada  "We're Canadians.  We HAVE to be polite"
Finger as332 at freenet_carleton.ca for PGP public key.