they should be fine together, but heres a little formula for finding out how many fish are in your tank.
take the surface area of your tank( length times width), then divide that number by twelve for tropical freshwater, and that is the max inches of fish you can safely have in your tank.
The reason that the inche of fish to gallon formula doesnt work is because surface area determines the amount of oxygen that dissolves in the water.
so for example. My ten gallon tank has a length of 20 in, and a width of 10. So multiply 20 and 10 and you get 200, divide that by twelve and you get 16.999999999 rounded out thats about seventeen inches.
all freshwater fish need about 12 sq in of space
all coldwater need27 sq in
and all marine need 47 sq in
sertain fish though, like anabantids(gouramis and siamese fighter fish) can live in low oxygen conditions. The reason for this is that they have an auxillary breathing organ called a labyrinth. thats why siamese fighters can live in small cups and such.
allthough your tetras and caes cant so i wouldnt advise over stocking
and the more tetras the better because the schooling effect is nice