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

Well does not really matter from a practical standpoint but might be
more convient I suppose. The main thing is not to allow something to
become plant limiting.
You are not going to beat the algae through nutrient limitation, you
can try and you can try.

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.

Ahh well, here's your issue:
CO2.
Directly poor to variations of good to low CO2 levels is a great way
to culture BBA.

Poor CO2 is 90% of all algal issues for folks using CO2 gas.

Keep the CO2 20-30ppm during the entire lighting peroid, check pH at
night(PM) and in the early AM. Make sure the CO2 is good during both
these high/low points.

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.)

Well here's what happened with your tank:
You added PO4, this drove the NO3 uptake rate faster, so the NO23
dropped to zero and the plants growth slowed down significantly. BGA
appeared.

If you had added more PO4 and KNO3, then the BGA would not have
occured.

The ratio in and of itself had nothing to do with it. I'd tell you if
it did, I promise

It was the actual levels(limited NO3)

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

No, you did good, the English version is up, but the reference for the
article cited is in German.

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'd do this:
COP2, then check it again and again till you go nuts and geel very
comfy with it being 30ppm or so.

Generally in 99.99% of all cases, the CO2 will appear lower than the
actual concentration if there is an errorin testing or some other
acid, stray current in the water.

That is the first order of business anytime you see algae or have a
growth issue with plants.

Poor CO2 will get any and everyone from Amano down to the newbie, to
myself.

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... :-)

You can do the estimative index and not bother testing if you wish, or
you can control it and double check your estimations and find the
rates of uptake.
You can also use the plants themselves as indicators.

Eg Riccia pearling is great for CO2.

I'd do this for your tank:
Trim all the alagae I can, prune, vac off any detritus on the gravel
surface etc,l net out any left overs.
Fluff the plants good.

Then do a 50-70% water change.

Add the macros back:
1.5 teaspoons of KNO3
1/8+ teaspoon of KH2PO4

The following day: 30mls of traces

Continue this routine till your 7 th day and repeat.

Dose the macros and traces every other day alternating.

If you have moderate or lower light, you can do about 25-50% less
dosing.

But the levels I suggested will be certain to address any non limiting
needs you might have at any light level.

Biggest issue for now: CO2.

Regards,
Tom Barr

Cheers,

Michi.