[APD] Re: PO4=algae?

[Thomas Barr <tcbiii at earthlink_net>]

> But as a true fanatic I always need faster growth,
> so I sometimes try to dose KH2PO4.
> 
> 310 litres, 0.7 watts/litre, pH 6.0-6.5,

This is a very big range.

alkalinity 2-4, total
> hardness 6-8.

Degrees I assume. So is it 2 or 4 or 3?

> KNO3, K2SO4, MgSO4, Micros as recommended.

You do not need the MgSO4, with a GH of 6-8 likely.

> The Fe fluctuates between 0.2 and 0.05 ppm between
> each wc (I dose twice a week).

Try 3x a week same volume but split it up more.
Also try adding the same amount 3x a week.

>The NO3 fluctuates
> between 5 and 15 ppm and I have a hard time
> finding the right KNO3-dosage. My fish seems to
> provide a whole lot of N (50 Rasbora espei,
> 7 Chocolate gouramis, 2 SAE:s, 3 Ottos, 2 Rams).
> The day after each KH2PO4-dose (0.5 ppm) my front
> glass always have considerably more algae.

I think CO2 is the issue, not the PO4.

When I had
> Cyanobacteria they really boosted with each PO4-dose.
> Especially if I forget to cover the aquarium at night as it
> otherwise gets direct and indirect sunlight in the mornings.

Well we see Cyano along many gravel lines near window light.
 
> The plants didn't grow remarkably faster with each
> PO4-dose. Perhaps somewhat more bud-development.

Well then something else is the issue then, not PO4.
My bet: NO3 or CO2. Most of the time, if folks are adding enough PO4/Traces,
they can look to these two.
 
> Question: Is it possible my plants get enough PO4 from
> my polluted substrate and therefore not take any PO4
> from the water column?

Not likely.
I'd look elsewhere. In any event, I can tell you the PO4 removal rate is
quite rapid and excess PO4 does not cause algae, folks have gone to 2ppm and
more and never had any. I've even heard of some folks going to 10.00ppm of
PO4 for the hell of it.

Try CO2, look at the levels critically, get a good test kit, make sure
there's enough for the _entire_ day length.

Advanced folks seem to get lazy and assume too much about having a CO2 level
IME. This includes myself but I am very aware of this. Also, NO3 test kits
really bother me. I've posted a number of times about it.
If you know what your tap water is, do those 50% weekly water changes and
estimate with the KNO3. If NO3 is building up, it's likely the plants are
not using the NH4 either etc.

If you have too many fish etc, this NH4 level is enough to cause other algae
outbreaks. Your bout with Cyano sounds more like you have too little NO3 and
you have assumed the test kit was correct.

I'd doubt the kit if that happened and the kit said 5-15ppm.
 
Regards, 
Tom Barr 
 
> // Daniel Larsson

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