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Algae and Tap Phosphates
Something I read in Tom's response during the other ill- structured exchange
has been hanging in the back of my mind all day:
> Date: Thu, 28 Dec 2000 22:37:49 -0800 (PST)
> From: Thomas Barr <tcbiii at yahoo_com>
> Subject: Re: DI/RO
> I have to add P to my water to **prevent** algae. So do
> many others. I use to be blessed with 1.2ppm PO4
> levels and now I have only .06ppm :(
> I hate having to add it. It sure helps though. There's no
> doubt at all on this issue. If your having algae issues
> on a well planted tank, I would be careful to blame the
> PO4. I did a water change and my plants grew like
> gangbusters and no algae at all...
This, of course, was in line with my comment concerning Green Water
outbreaks when the utility adds phosphates. But the situation does beg the
question, since it _is_ a recurring theme here in my tanks semi- annually,
so I'll just pop it in as another "topic".
The problem is that I'm not sure I can blame anything _but_ the added
phosphates in my case, but my reasoning may be faulty.
My approach to plants doesn't differ all that much from that of fish
husbandry when it comes to the water. Everybody gets a constant supply of
fresh water, simple as that. Seems to save me a great deal of time in that
the only real monitoring I have to do is in adjusting the initial
parameters. Any additional testing is usually saved for apparent problems,
although a few years' of practice do indeed give you an "eye" for what's
So I don't even try to "conserve" anything as far as resources go, as I'm
not concerned about depletion rates and the like. Nor am I overly anxious
about increasing concentrations of just about anything I put into the tanks.
My aim isn't to have a single tank's volume last me a good five years or so,
as has been quoted a couple of odd times by posters. Instead, I'm prone to
changing 15-60% of a tank's volume every other day (load- and species-
The _majority_ of my tanks run under local tap parameters, which to save
space here can be viewed at
on Tennessee- American's Web site. (Check out _those_ chlorine levels, BTW -
I certainly *wish* mine were the 1 or 2 ppm that so many people report.) As
you can see, our water's almost perfect for both plants and fish, with one
exception - potassium. I _do_ dose up to about 5 ppm there with the addition
of a 50:50 mix of KCl and KNO3. I add a single drop per gallon of Flourish
Iron, about once in a blue moon a little straight Flourish, and DIY CO2. The
CO2 drops the pH down to about 6.6 - 6.8, so CO2 might be running a little
above 20 ppm in a couple of the tanks.
All tanks are iron- and Osmocote- fortified litter with sand topping. Sand
depth can average from almost 3 to about 8 inches over the litter, and in
any tank with "diggers" they are prevented from reaching the litter layer by
The percentage of a particular tank's volume that is changed is determined,
as I mentioned, by the bioload balance within the tank. I figure the easiest
way to set the flora- to- fauna "interaction ratio" is to monitor for
nitrates and phosphates, so any time these figures get above my "setpoints"
(5 ppm NO3 _or_ 1 ppm PO4 - I feed heavily and heartily), then it's time to
increase the change- out percentage.
For 363 days of the year, these tanks are pretty stable, and not bad to look
at. Workloads are reduced to mere water changes and prunings - even
substrate siphoning is rarely called for. It's also rare for me to have to
clean even spot algae from the glass - a situation to which I've become
happily accustomed, and one which you'll never catch me complaining about
The tanks carry some hefty lighting levels, too, ranging from 60 W Fl over a
38- gallon (the Tanganyika tank I'm trying for algae with) to 200 W MV and
100 W Fl over a 55- gallon.
So that's about as complete a picture as I can paint of my normal situation,
save for one item. The odd two days of the year that they don't look so hot
are those two singular days that I come home from work to find a housefull
of green tanks. Checking the water, I usually find about 2.5 ppm PO4 - from
the tap. If you looked at the WQ report, you found that there's no mention
of phosphates. That's because it's luckily not a factor here, ranging at
close to undetectable and hardly worthy of mention. Except during major
seasonal changes, when the utility _purposely_ runs a phosphate through it.
(I once asked about the "phenomenon" and was told by TAWC that this was
intentional, serving a purpose that didn't register nearly as well as the
fact that they were, indeed, adding it.)
Now _everybody_ gets daily 60% water changes until the green goes away.
Normally it takes about 3 - 4 days for them to remain clear again, and
amazingly enough it's about the time the plumbing's finally flushing out,
too. And I'm safe and sane again for a few more months.
After a few years, I seem to have this "regional routine" down pretty pat.
Still, Tom may be correct - perhaps I'm cruising through the easiest
assessment of the situation. But it's the only thing I can find with any
connection to all of the affected tanks (those that _don't_ go green aren't
supplied with tap - they start out from RO/DI).
There's the scenario, tossed out for open debate. If I'm going about it the
wrong way, don't hesitate to say so. If there's a way to _prevent_ it, then
I'd definitely love to hear it...
David A. Youngker
nestor10 at mindspring_com