" wrote in message
om...

Aquatic macrophytes are not marine phytoplankton which is what the
Refield ratio is based on. the avwerage of most submersed plants is
10:1m, not 16:1.

Ah, I didn't know that. So, we'd need to shoot for less nitrogen and
more phosphate than this calculator recommends?

It also wrongly assumes BGA will be caused and cured within pretty
narrow ranges for NO3 and PO4.

I can assure you that I can have a 2ppm of PO4 and 5ppm of NO3 and
never get BGA outbreaks. Likewise I can have a .2ppm of PO4 and a NO3
of 20 and never get any.

I believe that. Personally, I'm actually more interested in keeping other types
of algae down. Black brush algae (the bane that caused me to tear down
my tank eventually and start again) and, to a lesser extent, beard/staghorn
and green thread algae.

BGA will appear if you drop the NO3 levels down very low and slow the
plants uptake(perhaps of NH4 and thereby allowing the BGA an easy
meal, they do not need hardly any N relative to plants)

Yes, seems that way. The Redfield ratio indicates that high phosphate and
low nitrate favours BGA, and high nitrate and low phosphate favours
green algae. (This agrees with my previous experiences -- I was battling
green algae until I picked up on your recommendation to dose phosphate.
Unfortunately, by the time I saw the truth, it was a bit too late to save the
tank.)

The reference is also not for FW, but rather phytoplankton. While I
cannot read German/Dutch, I can tell from the names and it appears
that they did not add plants to these experiments, only algae.

Me bad -- I posted the wrong link. Here is an English version, which
I'm sure will make a lot more sense to many people :-)

http://www.xs4all.nl/~buddendo/aquar...dfield_eng.htm

Add some KNO3 at 1/4 teaspoon per 20 gals 2x a week if you use CO2 or
more depending on lighting/fish load. That alone will keep it away.
See APD for older post about BGA and heterocyst.

I've just (a week ago) set up the new incarnation of my tank. (150gal nominal,
actual water content 130gal.) I've been following your posts on APD about
whether to fertilize a freshly set up tank and started dosing KH2PO4 and
KNO3 from day one as you recommend. So far, things are looking good.

I've been aiming for around 10ppm NO3 and 0.5ppm PO4. (It's difficult to
be precise with the test kits that are commonly available in Australia -- the
resolution isn't good enough. It turns out that LaMotte have an Australian
distributor though, so I think I'll get the high-resolution LaMotte NO3 and
PO4 kits, so I can control the ratio more precisely.) A very small amount
of green hair algae is currently present in the tank, and a little
beard/staghorn
algae, which I suspect I imported with the plants initially. I've been removing
what I can find of those manually. For the time being, the only fish are a
bunch of Otocinclus Affinis that are not getting any food other than what
they can find for themselves, in the hope that they will stay on top of any
minor algae growth. We shall see... :-)

Cheers,

Michi.

--
Michi Henning Ph: +61 4 1118-2700
ZeroC, Inc. http://www.zeroc.com