# RE: Hatching Nothobranchius and etc.

• To: <killietalk at aka_org>
• Subject: RE: Hatching Nothobranchius and etc.
• Date: Thu, 24 Apr 2003 12:51:48 +0200
• Thread-topic: Hatching Nothobranchius and etc.

```> From: Drummond Howard [mailto:drummondhoward at hotmail_com]

> Isn't the speed of light limit theoretical as well?

No. It is experimenatally verified: 300'000'000 m/s. The whole e=mc^2 bit is theoretical but seems relatively water tight...

> From: Wright Huntley [mailto:jwwiii at pacbell_net]

> What? Why on earth do you make that claim? Pressure doesn't  give a hoot
> whether it is in a gas (air), liquid (water, egg) or solid  (bar of steel).

Remember the physics? Pressure = density x height x acceleration due to gravity... the phase of the substance does have effect on pressure. I little pressure on a gas will have much LARGER effect on volume than the same amount of pressure on a liquid or solid but this is irrelevant as you correctly point out. One Atm of pressure is 1 Atm of pressure whether it is above or below water. And as also demonstrated the pressure changes with depth. Because water is denser than air you will get a larger increase in pressure for every meter you get deeper.

Some one pointed out that at 14 inches you accomplish a 1 psi change in pressure which some would hold significant as you get better hatches. 14 inches is quite a lot of water. Over a foot deep. Lets assume the notho pond has a surface area of say 100 square meters and the depth was uniform all the way through. That is 35000 L or 9210.5 gallons. That is a lot of water. I doubt after the first shower the pond is filled up. I doubt a depth of five inches is reached let along 14.

If pressure was such a big factor why do wet wet our eggs in shallow trays? Deep tanks don't work.

I will not deny that the anecdotal evidence says something is happening for the better but the explanations don't fit the natural situation. Pressure is not the real factor changing to give better results.

> From: Mark Mackenzie [mailto:mark at mackenziesystems_com]

> One of those triggering components could ... added
> oxygen.  In the clouds ozone mixes with water and makes  hydrogen peroxide
> and oxygen, H2O + O3 = H2O2 + O2... So
> when the rain reaches the ground it mixes with salts,  destabilizes the H2O2
> and adds some more O2 to the water.  Could be why the  oxygenated water and
> H2O2 work.

Rain water has a higher disolved O2 and CO2 level than water left to stand. By increasing the pressure of the hatching container you do indeed increase the activity of the dissolved oxygen and other gasses. As the gasses compress with the increase in pressure a new equilibrium is produced between the gas and the water. Because of the increased pressure more gas dissolves into the water.

It was mentioned that an airstone will helpt with bellysliding. I don't know how. The airstone will drive off most of the CO2 and get rid of any extra O2. The use of an airstone conradicts what is going on in this thread...

> From: John N. Alegre [mailto:listhub at andante_mn.org]

> What the real effect of oxygenated water, if any, on  prevention of belly
> sliders is certainly unknown.

There is nice scientific answer to the debate.:-)

> I have has a few tetra people  tell me that it
> has to do with the amount of O2 available to fill the swim  bladder.  This just
> appears to simplistic for me to believe.

The fish would be able to adsorb O2 from their guts for respiration which makes the whole idea that they use O2 to fill the swim bladder a bit strange. They would use this O2!!! The swimbladder would best be filled with other gasses.

>  I would suspect  that it is something
> to do with higher 02 in the surrounding water leading to  higher 02 in the fishes
> blood.  This should facilitate the final stage of ATP levels by simple
> stoicheomitry at the mitochondria F1 membrane complex but  this is just a pure
> guess.

It is the most sensible explanation so far with the physiological implications. More O2 means better respiration and more energy (ATP). In an environment with very little O2 the fry would be stressed and probably not be able to fill their swim bladders. Increasing the pressure means more O2 and other gasses reach the fry making it less stressed and stand a better chance of filling their swim bladders.

Getting back to why we generally hatch fry in shallow tubs... If we had an airstone in the tub the peat would go everywhere and we wouldn't be able to see the fry. Also the current would weaken the fry and probably kill them off as they struggle against it. So we use shallow tubs because shallow tubs will hold more O2 than a deep tub, or rather they will have a more uniform O2 concentration.

So will adding O2 to the hatching tub or keeping the eggs under pressure give better results? All the reported data say "yes". Some may argue that this is all anecdotal, well sometimes anecdotal evidence is the best kind and when you have enough observations you can put together a half way decent hypothesis. Wether you like it or not a lot of our scientificly derived 'facts' grew out of anecdotal evidence. They became scientific facts because some guy with time and money could go out and test the observations.

Anecdotal evidence is no less valuable than scientific evidence when it comes to finding out the truth... although experimental data can't be beat.

tt4n