Re: Calcium/carbonates again (was Re: Deformed Rainbow Fry)

Peter Hughes (peterh at pican.pi.csiro.au)
Thu, 14 Nov 1996 10:17:15 +1100 (EST)

I agree with you in general terms Simon. However many of the people on
this list and most of those likely to be in a position to test this would
not have the equipment, time, or perseverance to do the test properly.
Truth be known it would really take at least three replicates and
hundreds of individual juveniles in each test and then how do you measure
the success? Number of fry, percentage hatch rate, growth rate, median
time to a particular body length? The sort of thing I suggested was so
that if the effect was really big we could get an idea and if it was not
then it is of marginal use anyway.

Talk to yo later

Peter

On Wed, 13 Nov 1996, Simon Barry wrote:

> Peter,
>
> > This is still not a brilliant solution as the hardness changes
> > continuosly. What we really need is for someone on this list who has had
> > success with the shel grit method to set up two tanks with eggs split
> > from the one spawning, add CaCl2 to one and NaHCO3 to the other. Then we
> > may finally be able to work out what Roy and Gary have been argueing
> > about.
>
> This design is not the best. The effect of the different tanks is totally confounded with the water treatment. It thus does not provide a useful comparison as we cannot determine if any observed differences are due to the differences in tank position/

temperature/size etc or the water treatment.
>
> A better experiment is to replicate the tanks, for example treat two tanks with CaCl2 and two with NaHCO3. We can then compare any differences observed with the tank to tank variation. This will allow us much greater confidence in assigning the water

treatment to any observed differences in rates of deformity.
>
>
>
> > if you wanted it could also be extended to include four tanks, one
> > plus and minus trace elements for each treatment.
> >
>
> See above.
>
> Cheers
>
> Simon Barry
>