All the parts you will need (most of it comes in an Under Gravel uplift tube pack).

First take the bottom widened section, cover it with
flyscreen or netting and secure with a rubber band or three. I do this so fish
cannot get close enough to the eggs to suck them through the mesh. Cut off an
inch or so of tube and put it in the top of that part. Put a piece of netting on
top of the tube and one of the joiners over the netting to create the “bed” for
the eggs while keeping them in full view the whole time.

Cut a length of tube 3 to 4 inches long and place it in
the top of the joiner, making sure it seats firmly into the
joiner.

Attach a suction cap (heater holders are the
best).

You can make the rest of the tumbler before this next
step, but I’ll show you it anyway. Once the first section is made, you can
attach it to the inside of the tank with an inch or so protruding from the
water. Strip the female (or if it was an accident, collect the eggs) and place
the eggs / fry in a drinking glass, filled with tank water. Gently pour the eggs
along with the water into the tumbler. Don’t panic and tip them in too quickly.
Do it gently and if they don’t all come out, add a bit more water to the glass
and try again.

Next make the top half of the tumbler. Cut another 3 or 4
inch length of tube and place a piece of netting between it and another
joiner.

Attach another suction cap to this top half.

Take a length of airline and pass it through the air
exhaust piece, and place an airstone at the end that will be inside the
tumbler.

Place the airline, airstone and exhaust piece onto the top
piece of tube.

Place the top half onto the bottom half (with the eggs in
it) gently, and slide the whole lot down the glass until the top of the tumbler
is at least an inch under the surface. Turn on the air and adjust the distance
between the top of the tumbler and the airstone. The exhaust piece airline hole
should be a snug fit around the airline. If not, wrap a rubber band around the
airline when the airstone is adjusted. The higher up in the tube the airstone
is, the less water will be dragged across the eggs. Adjust the airstone height
until the eggs are constantly moving, but not lifting up into the air (well not
up into the water!)

Here is a completed tumbler. Easy! Notice that the exhaust
is facing away from the suction caps. You want the air to escape into the open
tank, not up against the glass.

Once the fry hatch, you can leave them in the tumbler
until their egg sacs are gone. Ensure to remove any unfertilised eggs from the
tube or you will risk killing the hatched fry. Unfertilised eggs will turn white
and grow fungi if left alone.