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A 10 is going to be too small for a trio long term, even just for temporary holding you will probably have to cram it with caves and plants. You may want to look into a 20 long which I would say is minimum for a trio and your fish will be more comfortable.
I have to agree with Phil. Male A. rupununi easily grow over 3"/75mm SL. Females are rather territorial. A 10 is just too small for a trio. If you are an experienced cichlid keeper, however, you should be able to keep a pair in a heavily planted tank if you keep an eye out for aggression.
The steindacheri definitely will not work the get about 4 inches. You will really only be able to get away with a pair of fish in a 10. Something smaller like borellii might better suit your needs.