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Re: Live Foods Digest V2 #108
Toan T. wrote:
> I read that this is not good for fish. Somewhere, it said
> something like; Don't use the regular water softeners
> from your Home Depot. They lower hardness by using (or
> adding, I don't remember) salt. I am thinking of DI,
> doesn't that stand for deionization? In ion exchange, is
> NaCl exchanged for other minerals that constitute
> hardness? won't NaCl itself do this?
You are right! The way ion exchange works, is to EXCHANGE sodium ions
for calcium ions (and any other polyvalent ions). For each calcium ion
you exchange two sodium ions. The rest of the compound stays the same
i.e. calcium carbonate changes to sodium carbonate & magnesium sulfate
to sodium sulfate, etc.
To effect such an exchange you need an "ion exchange resin". The resin
has a finite capacity. Once it is exhausted, the resin stops working
until it is regenerated.
To regenerate a "household" ion exchange resin (there are other types of
resins), it is washed with a strong salt solution (NaCl), then the salt
is washed out & the cycle begins all over again.
The product water has NO hardness, but substantially more sodium
compounds than you started with! Is this significant? Roughly speaking,
if you had, say, 300 ppm calcium hardness, now you have about 300 ppm
additional sodium compounds in the water. Not very salty, I think,
because sea water has about 3.5% NaCl (= 35,000 ppm!).
Now, whether it is harmful to fish, depends completely on the fish! With
killies, you ADD salt, as you do to the water of some other fish. With
discus - I don't have the slightest!
> > Another method, if you have HIGH hardness, say over 350 ppm, > > > is to let it just stand for a week or so & you will see CaCO3 > > precipitating .... It will soften the water somewhat, > > depending on exact conditions.
> I think my water is around 18 degrees dH, which translates to > about 321 ppm, as in your conversion factor. I am trying to > lower that to about 100-200 ppm. Is that possible with this > method?
Not in practical terms, i.e. without additional equipment, such as a
nitrogen cylinder, pressure regulators, etc.
> I am just wondering though, because I am going to be doing > frequent water changes, this would probably prove impractical. > I've tapped into my cold water pipe. I am going to add an > automatic water changer; either straight from the tap or by > using waste RO water (doesn't produce enough good water for me > AND the fish).
If you have municipal water, it probably has a significant content of
either chlorine, or chloramine. Thus by changing water straight from the
tap, you would be introducing it into your tank. Admittedly, a 15% water
change is not going to kill your fish, but I suspect that it will
needlessly stress them.
> The advantage to waste RO is that it is virtually free of > chlorine and chloramine, I think.
Not, unless you have a charcoal prefilter.
> The disadvantage is that it has a slightly higher hardness. I am > thinking of a 15% change per day, continuously. Any thoughts on > this.
If I understand you correctly, you seem to want to soften your water,
but then to use the waste RO stream (harder than your tap water) to
change the water in the tank? - "It does not compute!"
> > Another method, probably the cheapest, and the one used by > > municipal water works, is quantitative addition of "hydrated > > lime" - calcium hydroxide ....
> Sounds great, but, is it safe for the discus I am going
> to get? I am thinking that if it were used by water
> suppliers, then it has to be safe for humans, and would
> probably be safe for fish too. Am I correct? Where would
> I acquire this compound? It would be quite interesting to
> experiment with this product.
Because of the chemistry involved, I would think that water softened by
precipitation would be better than, say, RO water, because trace
elements are less likely to be removed as thoroughly as in the RO
process. (I am assuming, that trace elements are important to fresh
water fish, as they seem to be to salt water fish.)
BUT - and this is a very strong BUT - unless you can accurately
determine HOW MUCH calcium hydroxide to add, better leave this method
alone! If what I read is true (I have never kept discus) you CAN (and
probably will) kill your discus with alkaline (could be even STRONG
alkaline), hard water, which will result IF you overdose with Ca(OH)2!!!
> > Re interference of peat-treated water in measuring CO2 - it > > probably depends on the method. The method Im am familiar with > > is titration. Peat extract WILL interfere with it!
> titration? what is that?
Titration is a method for quantitating (determining the amount) of
various compounds in solution. It is usually accomplished by adding
DROP-BY-DROP a reagent from a burette (a tube that has volume markings
on it) to the solution you are titrating and at the same time watching
an INDICATOR present in that solution. The indicator tells you when to
stop adding the reagent and read off the amount added. If you are
determining hardness, by adding the EDTA solution drop-by drop, you are,
in effect, titrating.
Manual adding of drops of a reagent is for us, the poor folk :-(
Affluent fishkeepers can afford an automatic titrator (~2,000 & up)