The international duo join Jonny Gray in departing Scotstoun at the conclusion of the current campaign, with Dave Rennie and Jason O'Halloran also moving on at the end of their contract with the club.
Capped five times by his country, Australian scrum-half Frisby made his Glasgow debut in the first match of the 2018/19 season away to Connacht
The 27-year-old has since gone on to make 21 appearances in a Warriors jersey, the most recent of which saw him feature off the bench in February's victory over the Dragons at Scotstoun.
The former Bordeaux and Reds man has also touched down for four tries in his Glasgow career to date, including three tallies over the course of the 2019/20 season.
Tongan international Halanukonuka has turned out on 31 occasions for the club since his debut against the Ospreys in November 2017, with the tight-head having joined the club from Super Rugby outfit the Highlanders.
His sole try for the club came in a home victory over the Cheetahs in February 2018.
The 33-year-old's last ran out in a Glasgow shirt in the 2019 Guinness PRO14 Final at Celtic Park, a calf injury sustained shortly after returning from Rugby World Cup duty having prevented him from making an appearance so far this campaign.
Speaking about the pair to glasgowwarriors.org, head coach Dave Rennie said: "Nick and Siua are great men and have both given a lot to the club.
"When Nick first joined us, the boys took to him immediately. He has a great sense of humour and fitted seamlessly into our culture. He's one of our fittest players, has a really strong work ethic and has impressed with his drive to be better each day.
"He battled for consistent game time, as our two international nines (Ali Price and George Horne) have been playing so well over the past couple of years. However, he has both learned from them and helped them develop. He is a great club man and will be missed.
"Siua is an outstanding tighthead prop with a great set-piece skill set. He is very quiet and unassuming, but over the past three years he's put in a great shift in the front row.
"It's a disappointing way for Siua to potentially finish, having injured his calf one week after returning from representing Tonga at the Rugby World Cup and having just recovered prior to the suspension of the league. His attitude while in the recovery group and contribution to developing our young props has been fantastic and he has given a lot to the club off the pitch in recent months. We wish Siua all the best for the next phase of his life."