Re: Test kits Question

["David A. Youngker" <nestor10@mindspring.com>]

From: Erick Jones
Sent: Monday, October 11, 1999 1:51 PM


> Someone please enlighten me. I know that conductivity is,
> Its the measurement of waters ability to conduct electricity
> this will go up and down as salts (of about any type) is
> added or subtracted from the water. So while I have a basic
> understanding of what it is, I just need someone to explain
> the significance of this parameter, and what the effects on
> apisto's are. Also how would one go about manipulating/
> maintaining it? Thanks in advance

Conductivity meters, in giving you a reading of the electrolytic level, give
you a firm handle on what's known as Total Dissolved Solids (TDS). Its
importance lies in its effects on osmosis, both in the regulatory functions
of the fish and, more importantly, the viability of the eggs.

The reason you normally see a hardness level listed with any referenced fish
in something like, say, Baensch, Andrews, Axelrod or any other text is
because the fish has evolved to live in waters of certain values. Two
*extreme* examples, of course, would be an Apisto and an Anemone Fish, but
even in various freshwater systems there are differing degrees of
adaptation - like with Lakes Malawi and Tanganyika. This is because osmosis
relies on *pressure* differentials in order to "balance" out the
concentrations on both sides of any permeable membrane and fish have
developed appropriate mechanisms to deal with either the absorption or
depletion of fluids and ions resulting from these differentials.

Adult fish have a series of adaptive measures that allow them to cope with
changes in salt levels other than simple fluid retention or salt excretion,
but chief among them is, of course, the renal system. An egg, however, has
nothing more than its outer membrane to provide *any* protection from the
environment, and that membrane *is* permeable to fluids. Since the topic is
centered around Apistos, then the situation most common in the tank is that
of an egg "designed" for softer water than that actually containing it. The
tendency here is for the egg to lose water to its environment, thus
contracting and thickening the membrane. A "little off" and all you face is
simply a slightly tougher membrane. This could cause difficulties in
everything from the sperm's penetration to the embryo breaking through at
hatch-out. But a lot off and you toughen it enough that even oxygen can't
pass and the embryo suffocates.

The opposite occurs when you take, say, a Julidochromis egg and try to keep
it in too soft water - the egg will gain fluid until the membrane fails in
the extreme.

The breeding fish also has the ability to "sense" the overall salt levels of
its surrounding environment, most likely through stress levels keyed to its
nervous and endocrine systems. When the environmental cues tie in with the
"ease of living" factor a closer match produces, the fish reacts through an
increased desire to procreate. Hence the "spawning triggers" we look for in
trying to produce a clutch.

Salt levels are easily controlled because they are linearly proportional.
Translation: if the levels are off, they can be changed by simply adjusting
the salt-to-water ratio. Adding an equal amount of pure water will cut
concentrations in half while adding an equal amount of salts doubles their
concentrations. TDS levels are perhaps the easiest-to-control parameters
involved in producing desired water types.

There has been some serious speculation of late that ties particular salt
concentrations to the spawning triggers. The most notable of these is
calcium, and to a slight degree the magnesium often associated with it. But
again, determining and affecting the concentration levels of even specific
salts is easy to calculate and involves simple ratios...

-Y-

David A. Youngker
nestor10@mindspring.com
http://www.mindspring.com/~nestor10






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