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Re: Nutrients


Jamie wrote:
> Thanks for the reply, Steve.
> Well...., I didn't want to bring it up, with the risk of being labeled a
> "bad" aquarist, but here it goes. My paludarium (frogs and newts) is usually
> passed up when weekly maintenance comes around, and here lately I had passed
> on it way too often. The hydrocotyle and riccia grow at exponential rates,
> all the time. No algae on the glass or on any of the plants. No algae
> eaters, not even MTSs. I hardly ever change any water and usually just top
> off any evaporation. On a whim the other day, I brought in a sample of my
> paludarium water. I ran PO4 and NO3 on it and was floored!!!!  (Embarassment
> setting in...) The PO4 was ~5ppm and the NO3 was ~250PPM! I about fainted.
> That's right, 250. The hydrocotyle (as you can imagine) is blooming every
> other node and the riccia is piling up.

So what else did I have lots of in my 90 gallon tank as well? Pennywort and
Riccia. Lots of blooms as well.
Don't worry about being a "bad" aquarist, we are all heretics pretty much
here:) Myself perhaps more than most:)

 So, I never expected anything of
> being out of whack.  There's always been a little earthy-smelling BGA on the
> wettest rocks (above water), but never any below the water's surface. Now,
> two weeks later, NO3 is ~25ppm and the PO4 is ~0.5-1.0ppm. All my little
> creatures are in fine shape and eating like lions. That's the problem,
> though. I feed the frogs and newts nightcrawlers and crickets from the bait
> store, but only once or twice a week.  Shamefully, I will keep a better eye
> on the tank.
 
> I have a weak solution of potassium phosphate monobasic, and I usually dose
> about 0.050ppm every two weeks or so. I was scared to use it more often or
> to use more, since I already had some spot algae. I thought it would only
> increase the algae population. More nutrients=more algae. I guess it
> couldn't hurt to try. I'll observe any changes over the next few weeks and
> report back and findings: good (hopefully) or bad. I keep K levels around
> 20-30ppm, so PO4 is all I'm lacking. Honestly speaking Steve, this is my
> only PO4-limited aquarium. EVER! I've always fought to keep PO4 levels down,
> I've done it for years and years. Adding PO4 now is like sticking my hand in
> the fire. It just doesn't feel right ;-)...

Plant filters, I have a hunch will remove the PO4's as well. Either more
lighting/CO2 or get the plants above the water somehow. I think certain
plants will remove PO4's better than others but a general fast grower should
be fairly equal with another. Pennywort is a good example from Jamie's, my
tank and in nature(Abott's Lagoon, Pt Reyes-note all the dairy farms right
next to it). The 90 gallon tank had a 200-300 leaf pennywort top along the
back. Quite similar to Jamie's froggy tank.

The Green spot has stayed off my leaves and is only slightly on my glass so
far. No problem ...yet. PO4 is 0. I'm feeding lots(overfeeding) so both my N
and P levels will seem low even though there's a fair amount being added
daily. Food may provide the needed amount in many cases as with all the
nightcrawlers, crickets etc that Jamie fed to his tank. Adding the PO4 can
be another way but as Claus also pointed out the PO4 was sucked out fast,
within hours indicating that testing an amount may only be when there's
enough in excess to get a reading and how long after the food or the
chemical was added. When the plants are not "starved" for PO4 it seems that
they will not attack that chemical nearly as much but still do never the
less. I might not be able to get a good reading on my PO4 and my NO3 due to
this. The nutrients are consumed by the plants before they make it to the
column to be tested. Now this is a balance for sure.......I'd prefer myself
to have a more measurable method to make sure that the plants don't go
deficient. The chemical method can be an easier to hit range but after some
time it would seem to be equal to the food method. It just takes some
getting use to.    

> Recall that Karen's new water supply contains something just
> under 1 ppm of PO4, if memory serves, and she has not noticed any algae
> problems.  My current guess is that Marin County's 'Magic Water' for plant
> growing is due in part to small levels of PO4 in the water supply.

It was 1.12ppm PO4 and a KH of 5, GH of 9. The Hach kit that Steve has also
measured about 1.0 or so. The tank I had typically got about 50% or more
weekly water changes and had a reading of .5-.6ppm after 3 days. I measured
further on Steve's idea.
PO4
1 day=.8ppm
2 day=.6
3 day=.4-.5
4 day=.3
5 day=.1
6 day=.0
7 day=water change 

NO3 average 10-20-ppm. FWIW I have stated in the past a NO3 level of 75ppm
for a few weeks with no algae but at 5.5 watts a gallon and lots of all the
other nutrients. And again those big water changes.
I have not added any extra PO4 yet now that I no longer have magic water as
Steve likes to call it. The PO4 here  were I now live is 0.06ppm compared to
1.12ppm. KH is now 6 from 5.

I would like to do an hourly test based on a starved tank(one week no PO4)
bring it up to .2 and then wait a week at 0,up to .5 then wait a week at O-
to 1.0 wait a week at 0 ,and then to 1.5 etc using a chemical for PO4 and
seeing by the hour the drop off. It may take awhile for the other higher
levels to drop off. I need to see if anyone's done such a an experiment
hydroponically etc. I could do this for pennywort or some other fast grower.
It would not prove it but would be very good evidence I think.
> 
> When we get together out here one of our recurring themes is the possibility
> that the Sears/Conklin conclusion should be reformulated as follows:  We
> reduce algae not by limiting P, but by assuring that N does not become the
> limiting factor. 

You may recall that I have been playing with lowering this (N03) and adding
it more in the form of food(NH4+). In lower lighting, I think this is not a
bad idea. Nor is the PO4 notion either............Higher lighting can be
tricky. A pack of shrimps/snails/SAE's sure seem to help.
I think adding the KNO3 to the higher lighted tanks is a wise move but I am
trying to really consider what range of NO3 should be set. It's one thing to
add food or to supplement with chemicals, reliance on both can be difficult
to test directly so often I am left with the plant's themselves to make
assessments. I've had very high NO3 levels and really low ones and a few in
between. They are all manageable IMO. So what's all that mean regarding N?
There could be more to it than this. Perhaps the same is true of PO4. I
think you can use either one and also Fe as well as the limiting algae
controller. I t seems to really depend on how you want to balance things and
what routine works best for you.

 And we often note that some systems appear to benefit from
> the addition of small amounts of P every few days.

My plants always grew super after the water change similar to Claus's noting
above. Not as good down here but still good so far. Too soon to tell though.

Regards, 
Tom Barr