Discipline was a major issue for the Fijians, as they were given two yellow cards, which cost them the game.
Joji Nasova was shown a yellow card for throwing the ball away in the 7th minute of the first half, and Iowane Teba received a yellow card in the second half.
The Blitzbokers showed some impressive rugby as they continued to put pressure on the Fijians, making them commit a lot of mistakes.
Shilton van Wyk scored a double, while Selvyn Davids scored one try.
Fiji will face France at 9.27pm tomorrow in the 5th-place playoff.
In other results, Kenya beat the USA 26-21 in the 9th-place semi finals, New Zealand thrashed Ireland 42-5 in the 9th-place semi finals, Spain thrashed Uruguay 38-0 in the first quarter final, Argentina beat Great Britain 27-14 in the second quarter final and Australia beat France 22-12 in the last quarter final.
Spain will face Argentina at 7.05pm tomorrow in the first semi final, and South Africa will play Australia at 7.27pm tomorrow in the second semi final.
The cup final will kick off at 11.35pm tomorrow.
The Fijiana 7s will face Ireland at 11.03 tonight in the 9th-place semi finals.
The Women’s cup quarter finals will kick off at 12.02am tomorrow, the cup semi finals will start at 7.49pm tomorrow, and the cup final will kick off at 12.11am Monday.
Live Updates
Perth 7s: FJ vs South Africa Updates
Kick off: Fiji 1' Try to South Africa. Shilton van Wyk. FJ 0-7 SA
2' Try to South Africa. Selvyn Davids. FJ 0-12 SA
5' Fiji survives the attack from South Africa. Fiji gets a lineout and a chance to put points on the scoreboard. FJ 0-12 SA7' Joji Nasova shown a yellow card for throwing the ball away. FJ 0-12 SA
HT: FJ 0-12 SA
2nd Half
Kick off: South Africa
9' Iowane Teba shown a yellow card, South Africa given a penalty try. FJ 0-19 SA
