That is almost over stocking as it is.
A 20g high tank is the same exact footprint of a 10g tank. I know that the 2 first species need to have a 20 gallon long tank. Cory cats need to be in groups of 6+.
Back to the Serpa Tetras, They prefer water temperatures ranging from 72–79 °F (22–26 °C). They will live better and show off their best colors in soft, neutral to slightly acidic water. As with any other schooling fish, they thrive in large groups and should be kept in schools of at least six fish. The tank should also be well-planted, providing shelter and hiding spots.
Cardinal Tetra care:
https://www.seriouslyfish.com/species/paracheirodon-axelrodi/
According to Seriously Fish.com...
Temperature:
23 – 29 °C
pH:
3.5 – 7.5 although wild specimens do best in more acidic conditions.
Hardness:
18 – 215 ppm; towards the lower end of this range for wild fish or breeding.
You will have to ask
@Byron for any other extra information. IMO putting all of those fish in that small of a tank would be bad for their health. Try to look into getting a 20g long. There a lot more possibilities.