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Belly sliders


	 Lee Harper wrote:  

	  ... But, most people experience the reverse percentage without
the 'oxygen pills';
> so something is wrong with conditions that is compensated for by the
> 'oxygen
> pills'. The 'oxygen pills' are certainly worth trying, and I will, but
> I
> believe there is some other factor that is amiss, i.e., temperature,
> wetness,
> etc.
> 
	Yes, you are exactly right! Maybe I should try to summarize my
experiences about the belly sliders a little more in detail:
	I have been breeding nothos for several years and never had
problems with belly sliders. Then I started to breed Cyn. nigripinnis
and bellottii, and there I always got a high percentage of belly
sliders.  To avoid that problem I tried different incubation conditions:
I tried to improve the result by varying  the temperature (between 18 to
28 °C), the wetness (2 to 4 according to Langton), and the incubation
time. Particularly the incubation time I thought could be important
because I once read that if the embryo stays to long in the last
diapause, it can start to 'digest' non vital organs. (Meanwhile I doubt
this theory, particularly because the swimming bladder is definitely a
vital organ once the embryo has hatched...) 
	I have never varied the amount of air in the incubation bags,
but changing all the other parameters has not improved the outcome of
the hatching with respect to the belly sliders.
	Then I heard of the 'oxygen pill' method: In the article I
mentioned in my last mail, it's basically stated the following: The
Cyprinodontoides have no direct connection between the swimming bladder
and the digestive tract, therefore they cannot fill the swimming bladder
that way. But the swimming bladder is surrounded by a fine net of blood
vessels and is most probably filled via gas exchange. Therefore, a low
oxygen level in the water may hinder the fry to fill the swimming
bladder. (I should mention that this is maybe the weakest point of the
theory, because the direct correlation between oxygen content in the
water and oxygen content in the blood is certainly 'risky'.)
	The following 'observations' support that theory: Fry often tend
to go towards the surface. This is probably NOT to get 'a mouth full' of
air, because they could not break the surface tension anyway BUT close
to the surface the oxygen content of the water is usually the highest.
Further on, one often gets better results by the use of rather cold
water. Again cold water can dissolve more gases!
	From the people that told me the oxygen pill  method, I also got
the story that once a guy set up a system where he 'circulated' the
water of the hatching tank and let the water drop via several fine tubes
in the container where the water level was kept low. Like this he
'simulated' the rain, and got good results - again another way to
increase the oxygen level! 
	Personally I was at the beginning a little skeptic, too. To test
the effect of the oxygen pills, I split one batch of eggs into two
identical container, poured the same water in and added in one case the
oxyletten, in the other case not. In the first container I got 143 belly
sliders from 170 fry, in the one with the oxyletten I got 14 belly
sliders from 130 fry. 
	Finally I would like to comment the absolutely correct remark
that 'something else with my conditions must be wrong, because many
people have success without the oxyletten!' 
	First, it seems to be a phenomenon that depends strongly upon
the species. Like I mentioned before, with nothos I had never problems.
Second, and probably more interesting is the fact that I usually
'harvest' the peat from setups, where the fish have stayed in for
several weeks. I usually don't use spawning containers and seldom make
short breeding setups. As a result the peat - I use it as the ground in
the aquarium - with the eggs is normally strongly contaminated from the
adult fish. Then when I pour water over it after the incubation, I get
probably very fast close to 'anaerobic conditions' in the hatching
container. The result are many belly sliders. (On the other hand,
usually more or less ALL eggs readily hatch when I water the peat the
first time.)

	To summarize my point of view again: If you have no problems
with belly sliders, don't waste your time with oxyletten. If you have
problems, increase the oxygen level in your hatching container. One easy
way to do it is the use of oxyletten.

	Peter Uhlmann