I've got a pretty big tank and it's already set up and been running for about 2 years with successful fancy tailed guppies. My little sister just won a goldfish from a carnival and wants to put her goldfish in with my tank. Is it okay fro the goldfish to be in there? Will it hurt my guppies, will my guppies hurt it, and would it hurt the goldfish to eat the same kind of food as the guppies if it's okay to be in the tank? A fast response would be perfect, I really don't want her fish to die, but I don't want it to kill off my guppies either. Thanks in advance!