[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Aquatic Plants Digest V3 #909

Despite Steve's plea to the contrary, I'm going to combine a number of
responses into a single letter.  Just too many, and too many that I'd
rather not see extended to a sustained thread.

Dennis asked:

> There are graphs to show relationship between GH, pH and CO2 concentration.
> But does anyone have an actual formula to do these calculations?

The relationship is between alkalinity (KH), pH and CO2.  GH is not a
factor.  Formulae are available at the Krib.

> ------------------------------

David Ozenne wrote:

> Paul described how boiling water can reduce GH and KH by precipitating
> out CaCO3.  This got me thinking that you could perform ion exchange
> water softening by adding NaHCO3 and then boiling the CaCO3 out.  Of
> course, we generally don't want ion exchange in our hobby, because the
> sodium is undesirable.  So what about potassium?  Anyone know if
> KHCO3 is readily available?

This might work, but as George pointed out, the energy costs on something
like this are really exhorbitant.  I use 30 gallons of tap water/week for
water changes and there's no way I'm going to boil 45 gallons of water so
that I can decant 30 gallons of "softened" product.  This is just not
practical except on the very smallest scale.

> BTW, I was looking at the equilibrium equations and it seems to me
> that adding NaOH would have the same long term effect on your water
> (after re-equilibrating with atmospheric CO2) as adding NaHCO3.  Taking
> the following 3 reactions:

NaOH is lye - extremely caustic.  It is to high pH what hydrochloric acid
is to low pH.  Use it with great care and in small amounts.

There may be an increase in alkalinity but not as easily and certainly not
as safely as when adding a bicarbonate.

> ------------------------------

Bill Hamlin wrote:

> Ok!
> I am biting the bullet.
> I have pulled out my periodic table, blown the dust off and with grim
> determination settled in to finally figure out out this general hardness
> stuff.  Actually it didn't seem too hard if I am understanding it
> correctly.  But that is where you come in (if you chose to accept this
> mission).  I need someone to take a look at what I have scratched out.

[This is detailed, so most of you will probably want to skip on]

> Here it goes:
> 1 degree GH = 18 ppm CaCO3 = 18 mg/L CaCO3 = 18 mg/L MgCO3
> (I assume its the same for mg/L for Mg.) ???

This is true for MgCO3 as long as you realize that it represents the
magnesium as the equivalent amount of calcium.  Pretty indirect and
bizzare, all in all.


> Therefor
> 1 degree GH = (18 mg/L of MgCO3) * (24.3 units Mg) / (84.3 units CaCO3)
> 	    = 18 * 24.3 / 84.3
> 	    = 5.2 mg/L for Mg

A little more complicated than that, really.  The MgCO3 is represented as
the equivalent amount of CaCO3.  CaCO3 gives 50 grams/equivalent (that's
g/eq), and MgCO3 gives 42 g/eq.  ; 18 mg/l of MgCO3 as CaCO3 is converted
to the actual amount of MgCO3 with

mg/l MgCO3 = mg/l MgCO3 as CaCO3 * (42 g/eq MgCO3) / (50 g/eq CaCO3)

18 mg/L of MgCO3 (as CaCO3) = 15 mg/l of MgCO3.

Things are right from there out:

1 degree GH = 15 mg/l of MgCO3 * (24.3 units Mg) / (84.3 units MgCO3)
	= 4.3 mg/l of Mg.
> Now if I look to my water chemistry:
> Water Supply Analysis (City of Winnipeg)
> Total alkalinity	78 mg/L
> Total Hardness		76 mg/L
> pH			8.0
> Calcium			20.6 mg/L
> Magnesium		5.62 mg/L

Good water.

> I can calculate the GH as follows
> Calcium: 20 mg/L / 7.2 mg/L/degree GH = 2.86 degrees GH
> Magnesium: 5.62 mg/L / 5.2 mg/L/degree GH = 1.08 degrees GH
> Total: 2.86 + 1.08 = 3.94 degrees GH

Magnesium 5.62 mg/l / 4.3 mg/l/degree GH = 1.3 degrees GH

Doesn't really change the result much, does it?

> Now Steve P. recommends adding CaCO3 until you get 4 degrees GH so this
> should be adequate for most applications so my water should be pretty
> good right out of the tap (except for Chlorine and temperature of
> course).
> How did I do?
> Have I got the methodology right?

Pretty good.  Just remember the equivalents thing.  An equivalent is the
weight of an ion or ionic compound divided by the electrical charge on the
ion or compound - this is used as a way of comparing concentrations of
ions with different electrical charges.  In the case of CaCO3, the
molecular weight is 100 grams, there's 2 positive charges on the Ca (and 2
negative charges on the CO3), so 100 grams of CaCO3 is 100/2 = 50
equivalents of CaCO3.

> ------------------------------

Wayne Jones wrote (in response to Wright Huntley):

> <Power spectrum is (relative) Watts vs inverse frequency (or wavelength). All
> the
> <lamp outfits use that standard format.
> Not true. Every one I have seen has no units up the Y axis just percentage
> values. If you can direct me to charts that plot watts versus frequency I would
> greatly appreciate it.

He *said* relative watts.  That would be expressed as a percentage.

> <It *can't* be expressed in "lumens" vs frequency, for lumens -- by
> definition --
> <have a particular spectrum built in.
> This is of course quite incorrect. For any given freqency lumens can can be
> converted to either watts or PAR values. If you say spectrum charts are given in
> watts then they could be converted to lumens.

He was of course exactly correct.  Lumens are a broad spectrum measure and
the intensity of individual parts of the spectrum can't be
converted to lumens.  If you know what the spectrum is and exactly what
spectrum is used in the definition of the lumen then it would be possible
to convert lumens (or PAR) for one spectrum into lumens (or PAR) for
another spectrum.  That would be a painfully complicated conversion.

> <PAR is only a bit better, for it assumes a wider spectrum, but rarely does it
> <agree very well with the action spectrum of *your* particular plants, anyway.
> <Again, no such thing as PAR vs frequency. Same reason.
> Also incorrect. PAR and the visible spectrum are virtually coincident. Also, how
> can know that PAR agrees or disagrees with my plants since I cannot find out
> what what my lights are emitting. Again, you can plot PAR versus frequency. Same
> reason.

Again, Wright was very correct.  PAR is weighted flatly across the
spectrum that contains light useful to plants - essentially the visible
spectrum. But, its a broad-spectrum measure and not something used for
individual wavelengths.  Plants' response to light is not flat across the
visible spectrum hence we know that PAR doesn't exactly reflect light
intensity as seen by the plant.  It would be possible to devise a measure
similar to lumens that would be weighted to the action spectrum of plants,
and that would provide a more accurate measure of the efficiency of light
for use by plants.  Of course, different plants might be specialized to
use differently weighted spectra, so no one measure would be perfect.


> <Wrong. It gives us an excellent *indirect* clue. The good tubes that have lower
> <lumens/Watt are usually putting more energy in the ends of the spectrum where
> <plants are more growth active, and less in the more visible green region. Tubes
> <with high lumens/Watt will make the tank *look* brighter, but "feed" the plants
> <less.
>  Hmm let me think. Yes,  I believe you are incorrect. Typically plant and
> aquarium lamps that suposedly put out only in the red and blue spectrums are
> actually less effective at stimulating photosynthesis because their power output
> is actually lower in the red and blue spectrums than a lamp intended for the
> human eye. If only manufactuers would publish spectral charts in say,  watts
> versus "inverse"  frequency then this would be obvious at a glance.

Huh?  I don't think you're right that tubes specialized in red and blue
light put out less power in those wavelengths than do lights that are not
specialized in those wavelengths.

The available charts show relative watts vs wavelength.  All you need to
know to get what you want is the watts at 100%.  I doubt that you would
find that real useful, because the lamp output changes with use, and any
pure watts comparison you can make for new lamps may be wrong for lamps
under average conditions.

> <Read the spectra as *relative* Watts vs inverse frequency (or wavelength) The
> <peak is normalized to one, and all other values are just a percentage of that.
> <[Yes, it *is* frustrating that they assume you know that and never, ever label
> <the vertical axis.]
> What does this goofy chart tell you? Pretty much nothing. Who cares what the
> relative distribution is within a particular lamp. I want to compare one lamp to
> another.

I use the charts to compare spectral output.  If you want to compare them
otherwise, I suggest you either *ask* people about their experiences with
individual lamps, or use different lights and compare them yourself.

> ------------------------------

Bob Dixon wrote:

> Dave writes:
> <snip>>However, my search continues for a calcium supplement that will in fact
> >increase GH and not KH. Any suggestions anyone. Be careful, I will perform
> >the test.....
> I have fantasies of building an experimental CO2 generator using hydrocloric
> acid and dolomite, which will produce water and calcium chloride as
> byproducts.  Calcium chloride would do the job nicely.

Yes it would.  You can also buy calcium chloride cheaply as sidewalk
deicing pellets - at least if you live in that sort of climate.

> ------------------------------

And finally, Daniel wrote:

> They have
> 1 set of barbels not 2 and rest in diagnol position - this is a SAE right?
> the black stripe gos into the rear fin and seems to peter out. They also
> grab any flakes I feed to my tetras. For there length they are thinner then
> CAE's
> Someone confirm please!

Also check for coloration in the fins.  SAEs fins are all colorless except
for the bar extending to the fork in the tail.  Flying fox have dark
dorsal fins with a light or white tip, and "false SAEs" have dark bars
crossing the dorsal and may have red and yellow tints to the dorsal, anal
and pelvic fins.  They aren't necessarily thinner than CAEs.

True SAE's have been sold here as "siamese flying fox"

Roger Miller