yeah that's about 18 us gallons, so you need to aim for 18" of fish
you currently have
5 Tetra Neon's - 5"
2 Peppered Cory Cat's - 4"
3 Julii Cory Cat's - 6"
1 Guppy - 1"
1 Angel - 5"
2 Ancistrus - 6"
2 Bolivian Rams - 6"
1 Red Tailed Black Shark - not sure on the size.... but your already well over without it.
you probably have double the fish in there you should have, angels need a 40g min tank that's 18" deep so you need to re-home that.
i'm fairly sure the rtbs gets too big for your tank but do some research
i think you could get away with
5 neons
2 peppered cories
3 julii cories
2 bolivian rams
that's still overstocked but as it's spread around the different areas of your tank it should be ok