Using Insecticides

Are there pesticides or insecticides that are not as hazardous to the environment or pets?  My quince bonsai(4 years old) has black aphids, and I would like to use a non-toxic treatment for spraying this plant.  Some friends suggest a mild solution of soap detergent and water.  Do you think this is good?  Also, did I get the bugs by bringing the plant indoors for an extended time and lowering its resistance?