1. The homemade guppy isolation box requires a spare plastic bottle, as shown in the figure.

2. Next, cut the middle of the plastic bottle, as shown in the picture below.

3. Next, you need to make a safe passage for the small fish on the plastic bottle, as shown in the picture below.

4. Now take a look at the effect after the processing is completed, as shown in the picture below.

5. Next, place the processed plastic bottle head on the bottom of the plastic bottle, as shown in the figure below.

6. Finally, the homemade guppy isolation box is completed. See the picture below for details.