DIY Filtering aquarium with air pump

I use two plastic straws with diameters of 7 and 8 mm.

Buy an air pump on Amazon (paid link): 

https://amzn.to/3xowvwN

The thinner straw fits freely inside of the thicker straw.

The standard 5 mm diameter air tube fits freely in the straw.

Let's build a telescopic tube.
Wrap a couple layers of cotton sewing thread around the thin straw, making a ring, about 1 cm wide, closer to one end of the straw.

The thin straw should fit firmly inside of the thick straw.

Loop a rubber band on the thin straw to make a stopper.

Take a small plastic bottle with a cap.

Cut off the top of the plastic bottle.

Trim off the edges.

Cut off the bottom of the plastic bottle.

Trim off the edges.

Cut a strip from the edge to the center of the bottom part.
The cut should be wide enough for the air tube to pass through it.

The bottom part should fit inside of the top part of the bottle.

Make a hole in the cap using a hot soldering iron.

The telescopic tube should fit freely through the hole in the cap.

Use a needle, a nail, or a hot iron to make little holes about 1-2 cm above the cap.
Holes prevent water overflow.

Let's assemble all pieces together.

I use padding polyester to filter fish poop.
Wrap a strip of filtering fabric around the thin straw.

Push the roll in the cap.

Move the rubber band stopper to adjust the height - the straw should protrude above the roll.

Insert the air tube inside of the thin straw.

Put the telescopic tube in the aquarium, burying the bottom end in the gravel.
It prevents any fish from getting accidentally pumped out.

Connect the air tube to the air pump.
Turn the air pump on.
Move the air tube slightly in or out of the telescopic tube for a better pumping effect.

Cover the filter with the bottom part of the bottle to prevent water spills.

Rinse the filtering fabric under running water once a day. 

And then you can reuse it.
It is possible to use many commercial filters instead of padding polyester to remove unwanted chemicals.

This system can be used for filtering water, increasing oxygen level, and cycling water in any aquarium.
This is an example with 10 gallons aquarium.
Attach a paper clip to the rim.

Push the air tube all the way through the telescopic tube. 

Then, pull it back inside.

Feed the telescopic tube through the handle of the paper clip to secure the top of the installation.
Bury the bottom end of the telescopic tube in gravel on the bottom of the aquarium.
Attach the air pump and turn it on.

Put the cover on top to prevent water spills.

Here is another example.
I use a plant holder of wire to secure the installation in the middle of the aquarium.
It creates slow flow cycle.

Have fun and happy fish :)