Bruce
Here in the States, we are trying to do just that. The RSG has a program
in the works that will have its members list the species they have, what
sexes, and if they are breeding them. Then, through various incentives,
will attempt to get members to exchange their fish with other members, so
that the "threatened" ones are (hopefully) kept by enough people at any
given time to avoid loss to the hobby. Cary Hostrawser is "in charge" of
this monstrous undertaking, and I'm sure he can (or has he, and I've not
got the posting yet?) give the details much better than I.
Julie Zeppieri (RSG) <><From ??? at ??? Mon Jun 03 18:29:06 1996
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From: peter.unmack at ASU.Edu
Date: Sun, 02 Jun 1996 11:07:45 -0700 (MST)
Subject: RE: calcium (fwd)
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On Sun, 2 Jun 1996, Bruce Hansen wrote:
> <<If fry use up as much of the calcium as you suggest then it should be=20
> extremely easy to measure.>>
> I thought Peter Hughes pointed out that it would not be in the least =
> easy to do such measurements.
If the fish are using up that much calcium it should be detectable. ie,
if the fish only live in water at 50ppm or less and one raises the fry in
100ppm then I don't think the fish will use up all the calcium. If they
did use up the available calcium you should be easily be able to detect the
decrease if it is a significant one. If the hardness doesn't go lower
than 50ppm then it shouldn't be a problem. Again, this is confounded
since we can't split Ca/Mg and I am specifically referring to soft water
rainbows. I would still like to see someone propose a list of soft water
rainbows and hard water ones as that would help anyone who wished to test
the calcium theory compare hard vs soft water fish to detect any
difference in response to changes in hardness.
> BTW our water out here where I live is about 30 - 50 ppm generally but
Which is quite soft water. Melbourne water is a little less too being
around 20ppm where I lived.
> "available" and this covers not only the measured "hardness" or whatever =
> other parameter chosen but also the problem of Ca of Mg ratio could very =
> well be a factor. I don't know the answers Peter - we don't know what =
> form the calcium needs to be in for the fry to take it up. Perhaps like =
> in many animals other factors such as Vitamins D, C etc and perhaps the =
> ratio of calcium to Phosphorus also needs to be considered.
Talking to my Prof. Dr Minckley, he says fish can take up Ca from the
water as well as through food. He mentioned that there are some groups
of fish that are known to have problems in soft water. His first
question was what hardness is the water in the wild. If they live in
soft water then it probably isn't that important since they have done
just fine. He also suggested that there would be a big difference
between 10ppm and 100ppm and between 100ppm and 500 ppm but there would
not be much difference between say 100 and 200 ppm.
> Both authors assert that phosphorus (let's use P ) is likely to be a =
> limiting factor, so in situations where these deformities have occurred =
> we have to look at the "big" picture. Perhaps Roy's mineral blocks is =
> the best way to provide some of the necessary minerals but we will have =
> to look at P also.=20
P is limiting because bones are made of Calcium Phosphate I believe.
Thus you need a supply of both for it to work.
Personally I think the addition of some shell grit probably is beneficial
and I typically use it. I think Roys blocks are most likely better
again. I don't really think, or are yet to be convinced that it is
benefical due to adding calcium except perhaps in soft water. I think it
probably has other small effects such as buffering pH and just adding a
few other little "bits" to the water. Certainly, I don't think there is
any danger in adding it either. I just feel that if we can figure out
the requirements of the fry better we will likewise do better in raising
them rather than just plodding along in the dark. I would
suspect pH may have a greater influence (thus the potential buffering
advantage). This may only be crittically important in the first week or
three. Many people seem to raise fry in small quantities of water and in
my experience fry always leave food behind and many people avoid water
changing fry for perhaps a week through to 3 or 4 weeks perhaps. Thus,
there will probably be some shifts in pH unless the water is buffered.
Also, _most_ rainbows won't spawn in acid water, therefore it is possible
that the fry also won't do well especially in the first few days or
week in acidic conditions. I guess the confounding factor in this is how
much buffering do a few pieces of shell grit provide? Not much I bet
but I've never tested it and it may just be enough in those first few
days. One of the things that has always bothered me a little bit is we
tend to (from what I have seen) mostly raise bows on a carnivorous diet
(vinegar eels, brine shrimp etc) with very little plant material. The
Americans mostly use APR which may help the situation a bit. What do
people suggest as possible "green" fry foods? Obviously there is green
water, I've often wondered about crushing up some wollfia or the like
too. Do people think it is neccessary? Alternatively, am I just being
too anal retentive and just trying to fix something that isn't broken? :-)
Tootles
Peter