Among those arrested were two Canadians: Paul Ruzycki of Port Colborne, Ont., and Alexandre Paul of Montreal.
Australian activist Colin Russell was the first to have his case heard, as investigators asked St. Petersburg courts to extend the detention period for all 30. Six other defendants, including Ana Paula Alminhana Maciel of Brazil, also have hearings Monday.
During separate hearings two months ago on whether to jail the defendants, the rulings were the same in all 30 cases.
The Russian coast guard seized the Greenpeace ship on Sept. 18 and arrested everyone on board after a few of the environmental activists tried to scale an offshore drilling platform owned by Russian state energy giant Gazprom.
The detainees are charged with hooliganism, which carries a maximum sentence of seven years. They were initially charged with piracy, a more serious offence, but investigators have said that those charges would be dropped.
"I haven't done anything wrong," Russell, 59, told the court, adding that he did not understand why he had been detained.
His lawyer asked the court to free him on bail of two million rubles (US$61,500) or put him under house arrest in a St. Petersburg hotel. But the judge refused, saying if Russell was freed he could put pressure on the investigation or flee the country. He ordered him held until Feb. 24.
— With files from The Canadian Press.