23 inches by 12 inches. That is like a 15-20 gallon tank? I suck at math though.
Okay you listed:
1 pair angelfish
1 betta
1 pair tetra
1 pair coin
1 algae eater
Here is the problems:
The pair of angelfish need something no smaller than a 30 gallon tank. If the angelfish decided to breed they would probably kill anything they could in the tank in order to clear a breeding ground. In the wild they'd have a lot more room, but in captivity it is hard to provide them enough room to breed and not harm other fish in anything under a 55g, really.
As mentioned above, the betta shouldn't be kept with fish that have flashy or long or fancy fins
Tetras 99.9% of the time should be kept in schools of 6 or more in order to stay happy and stress-free.
I don't know what you are referring to by the pair of coins. Perhaps you could elaborate?
The algae eater... If it is a common plecostomus it will get to 12-18 inches in length and need something no smaller than a 55g, I would keep it in a 75g or larger at full size so that it could turn around more easily.
The fancy goldfish: Goldfish are temperate water fish and need water temperatures colder than that of tropical fish. For that reason they should never be kept in the same tank as tropical fish.
Your tank is severely overstocked with the angelfish, tetras, betta, algae eater, whatever the coin fish is, and fancy goldfish.