Aiken had five birdies to go with eagles at Nos. 3 and 11 and a one-stroke lead over Retief Goosen and Jaco Ahlers.
Michael du Toit, Dean O'Riley and Phillip Price are tied for fourth at 7-under 66 and six other players are at 6-under.
Aiken and Goosen played in the same group Thursday and Goosen opened at the ninth hole with a bogey. However, he ran off five consecutive birdies over Nos. 11-15 and put up back-to-back birdies at 18 and 1. He added birdies at 3 and 6 for his 65.
Aiken had an eagle at the par-5, 527-yard 11th hole but didn't catch Goosen until a three-birdie string over Nos. 16-18. He kept even with the eagle at the 492-yard third hole and moved ahead with birdies at 5 and 6.
Ahlers' bogey-free round included consecutive birdies at Nos. 12-15.