Re: Books, Phosphate, UG Heating

Karen Randall wrote:

> I have OFTEN seen cyanobacteria present even with high nitrate 
> levels.

Paul and I find that green algae predominates when nitrates are
available.  However, cyanobacteria seem to thrive where nothing
else can; if nitrates exceed 200ppm, or something else is killing
green algae (perhaps the copper in your local water?), then the
balance might shift back to the cyanobacteria.  I think that traces
of cyanobacteria are always present in a tank, but that when large
quantities of the stuff are coating everything (as seems to be the
case with Mr. Maladorno's tank), it's an indication that the phosphate
levels are elevated but the nitrate levels are not.

> In a tank 
> containing Discus, I suspect that the possibility of nitrogen 
> deficiency is somewhere between slim and none.

In a tank full of well-fed discus, the total amount of nitrogen
entering the system is quite high, but the amount of phosphate is even
higher.  Therefore, the plants run out of nitrogen (or K or trace
elements) before they run out of phosphate, and the free phosphate is
what's making the algae grow.  It follows that you need to add extra
nutrients to help the plants consume the extra phosphate.  That's our
hypothesis anyway.  More details are found in our paper, which you're
(hopefully) reading "as we speak".  Of course, the whole approach falls
apart if you don't have enough light to make use of all the available
phosphate, which can happen if you use phosphate buffers or get a little
carried away with the Pond Tabs.

> My tanks show _no_ measureable nitrate (low range test kit) and I 
> have tremendous grow with little algae.

If you're adding exactly (or nearly so) the amount of N required by your
plants to consume all the available P, you'll get good plant growth
with very little algae, and nitrates will be unmeasurable.  Paul and
I recommend a slight excess of nitrates to ensure that nitrates will
never be the factor limiting plant growth.

Yes, Paul and I are sticking our necks out by recommending that
nitrates sometimes need to be added to a tank.  Paul needs a shave

> (none on the plants, some 
> on the glass that is easily removed at water change time) IMO 
> recommending a nitrate level of 10ppm is asking for trouble.

I only recommend 10ppm because the first level on my test kit is
20ppm.  If you have a better test kit, 5ppm should be plenty.
I've pushed my nitrates up to 30ppm (accidentally) without getting
extra algae.

> Some 
> people, with other parameters just right, get away with it, but 
> I'm fairly certain that it doesn't contribute to good plant growth 
> as long as ammonium is available, and it _can_ cause algae 
> problems.

Nitrate by itself can't cause algae problems.  You need P (and K and
micronutrients) too.

> That's one reason that I wouldn't call the DIY fertilizer "poor 
> man's Dupla drops"... Dupla drops do _not_ contain nitrate.

You pay all that money for Dupla drops, and they don't even give you
nitrate?  I'd take them back for a refund.

How about Poor Man's Improved Dupla Drops?
Kevin Conlin   kcconlin at cae_ca   "We're Canadians.  We HAVE to be polite"
Finger as332 at freenet_carleton.ca for PGP public key.