OXYGEN

PERCH MAN

OXYGEN - An essential for most life on our planet.

By volume, our atmosphere has about 78.09% nitrogen, 20.95% oxygen.

The rest is made up of other gasses and vapours.

That means oxygen is about 21 parts per HUNDRED.

Water only contains about 8 parts per MILLION ! (8ppm)

(Think about this . . . Fish can survive on way less oxygen that we can.

This makes the DO (Dissolved Oxygen) in water critical for the survival of fish.

Get it wrong and you will end up with "white pond syndrome.

Find out below what "white pond syndrome" is.)

It contains this amount (8ppm) at sea lever, at 25C, without any disturbance.

In other words, if you left a bucket of water on the floor, at sea level, at 25c, with no bubbles or air flow over the surface, completely undisturbed, it would stabilize at about 8 parts per million.

When you add fish to the water then the oxygen is being used by the fish.

The more fish the quicker they use the oxygen.

Perch can tolerate quite low oxygen.

However, if you want them to grow at optimum rates, and get the best value for your food, the oxygen needs to be as high as possible.

During respiration fish, like other animals, take in oxygen and give out carbon dioxide.

The process is done by using gills in almost all fish although some can also use the skin and some have lung like structures used in addition to gills. With Australian perch the gills do all the work.

An important thing to know is that the higher the temperature, the less oxygen can be dissolved in the water.

See below.

If you have fish in your farm dam, and you suspect they are low on oxygen, all you need to do is add oxygen.

It's easy if you have a boat with an outboard motor.

Just run the motor at low speed so the propeller is moving the water.

The more you disturb the water, especially the surface the more oxygen will be dissolved in the dam.

If you don't have a boat with a motor, use any means you can think of to disturb the surface and move water from lower down across the surface of the dam.

The surface of the water is where most of the oxygen will be dissolved into the water, not because of the bubbles.

The bubbles do add a little as they move up the water column but the biggest job the bubbles do is, move the water from down below and cause it to move across the surface of the water.

The surface area of the water, (Where it contacts air.) is where oxygen gets into the water.

Also, other gasses escape through the surface.

In a commercial situation, in ponds, stocking density is very high.

If you get it wrong you risk "white pond syndrome."

You come out in the morning to find your fish are all dead and floating belly up.

The white bellies cover the pond and make the surface "white."