Re: [Killietalk] What's in my water

[Barry Cooper <bjc3 at centurytel_net>]

See any problems with that?

Yes. Plain salt (NaCl) will increase the osmalality of the water but lacks all the essential trace minerals that both fish and plants need. It is true that the fish might get some, or even all, of these in their food, depending on the food. I prefer not to assume that. You may run into problems with iodine deficiency (goiter) and other things.

A second point is that if you add only NaCl to RO water you will have NO buffering capacity and you will almost certainly get pH crashes as organic acids etc are added to the tank water by fish. You most definitely want some buffering capacity.

Therefore, in my opinion you SHOULD add back some of your tap water. The final buffering capacity and hardness obviously will depend on the proportion you add back. Do some experiments. Take a volume, say 1 liter, of your RO water. Add 10% tap water & mix. Test the alkalinity (buffering capacity) and hardness (using kits), and pH. Add another 10% tap water, repeat measurements. Repeat until you have parameters that are acceptable to you. I wouldn't worry if the pH is a bit high to start, as long as the buffering capacity is where you want it. The pH will undoubtedly drop once the water has living fish in it.

I am trying to remember why you don't want to use your tap water. I think you said that the hardness and alkalinity (buffering capacity, not the pH) had caused some of your fish not to spawn. If so, are you sure of the reason? Some fish, as well all know, like soft water, but it seems unlikely to me that many different species will stop spawning just because the water is a little harder. For my Nothos, I'd love to have harder water than the very soft water I have here. People say it is easier to add hardness to soft water than to remove it from hard water. It IS easier, but I'm not sure it's as effective. I'm not convince that adding back artificial additives to very soft, mineral poor, water truly emulates natural moderately hard water. I can tell you that I have never been able to emulate the success with breeding and raising my Nothos in the water I have here, even treated, compared to my experiences in upstate NY, where I had wonderful well water, with a TDS (conductivit!
 y) of 160 ppm. I never did a detailed water analysis there as I had no reason to do so.

Barry

Barry J. Cooper
Sweet Home, OR 97386



Edd Kray wrote:

>Putting together all this chemistry talk (good) with my question on RO
>water:
>
>I don't like the idea of adding any of my tap water back in because it's the
>Ca/Mg I want to make "go away" and it will put it back in along with the
>very strong buffering that keeps my water above 8.
>
>I don't like using some commercial product when no-one can tell me what's in
>it and what I'm adding back.
>
>Why not just plain Salt (NaCl), It'll give me a know chemistry, add back
>some ionic strength and conductivity, counteract osmotic stress and it's
>cheap (lots cheaper that a product like Equillibrium)
>
>See any problems with that?
>
>-----Original Message-----
>From: killietalk-bounces+edd=catfishnthecrawlers_com at aka.org
>[mailto:killietalk-bounces+edd=catfishnthecrawlers_com at aka.org] On Behalf Of
>Koran, David HQ02
>Sent: Friday, February 03, 2006 11:16 AM
>To: killietalk at aka_org
>Subject: [Killietalk] What's in my water
>
>As Charlie has stated you are measuring apples and trying to state the
>result
>as oranges.  When you measure conductivity this is a sum of a concentration
>of charges so to speak.  You sum the molal conductivities of the components
>of your solution.  Molality is a concentration term based on weight per
>weight, i.e., the number or fraction of atomic/molecular weights of an ion
>in
>a kilogram of water.  Molal conductivity is also a function of the charge of
>the ion.  To simplify matters you can approximate an average value for ionic
>conductivities and then use this artificial factor to relate the electrical
>measurement to weight of dissolved solids in your solution.
>
>To find the weight of dissolved solids you must eliminate the solution
>(water) or "dry the sample".
>
>Osmotic pressure is also the sum of osmotic pressures of the solution
>components.  In this case the component osmotic pressure is a linear
>function
>of the molality of the component.  The net directional flow of water across
>a
>permeable membrane (i.e., cell wall) is determined the net difference of
>component osmotic pressures.
>
>Hardness is a subjective measurement of the ability of soap in a water
>sample
>to form a lather or bubbles.  You can measure the concentration of
>multivalent cations in a solution by a "complexometric titration" and
>multiple by a factor to relate to hardness.  Hardness test kits add a simple
>alkaline buffer to your test solution and an indicator complexing agent
>which
>quickly binds to your multivalent ions in the test solution (that ions with
>a
>charge of +2 or more, namely calcium and magnesium but this will also hold
>true for iron and other metal cations which are probably in not much of a
>concentration).  When you add your 3rd solution you are actually titrating
>your metal ions with a more effective complexing agent than the indicator.
>This titrating agent is solution of a known concentration of EDTA (you see
>this in a lot of products! And is the chemical abbreviation for
>ethylenediaminetetraacetic acid which has 6 binding sites and effectively
>blankets each metal ion).  You add titrating solution until the EDTA
>scavenges every multivalent ion in solution and then out-competes the
>indicator for the metal ions it previously tied up.  At your end point or
>read out point you see a color change and that is when you have an excess of
>freed indicator (acid) over the metal ion-indicator complex ion.  You chose
>your indicator such that the color change (in solution) between the two
>forms
>is dramatic.  By rigging the concentration of solution you drop into your
>test solution to some concentration which is a multiple of what maybe
>doubling the volume (by addition of test solution) you can count drops and
>get an approximation of what the initial concentration of your multivalent
>ions were.  Remember, here again you have ions of different atomic weight
>but
>for simplicity sake you assume all multivalent ions you titrate/complex are
>calcium.  For the test kits you buy, calmagite is usually the indicator and
>in the free ionic acid form it is produces a blue solution (actually the
>conjugate base is a blue ion or absorbs light in all but the blue region of
>the spectrum) whereas when it is complexed with calcium ion it imparts a red
>color to water.
>
>Notice that in all of this discussion nothing was said about measuring
>monovalent ions or the ions of your akali metals; sodium, potassium and
>lithium.  It should also be noted that in measuring conductivity, calcium
>and
>magnesium ion will produce twice the conductivity of the akali metel ions.
>As hardness goes, it relates to the amount of multivalent ions present.  You
>form soaps and lubricants by breaking down polyglycols with a strong base
>(lye or sodium hydroxide) and form a salt of a fatty acid.  These soaps are
>much more soluble than the parent fatty acid but when paired with a
>multivalent ion like calcium or magnesium they readily form a precipitate
>and
>drop from solution.  You, therefore, don't simulate hard water by simply
>adding salt, i.e., sodium chloride.
>
>I know, ack, chemistry lessons on a Friday afternoon...you can now look for
>your beer.
>
>Dave K 
>
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>
>  
>


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