It was the council's first mayoral relief fund since 2007, when $310,000 was raised for 39 families whose homes had been damaged by floods.
Mr Brown promised to make a personal donation to the fund and urged the public to do the same before March 6.
"We can't bring Prickles or William back, but we can try to make life a little easier for their families."
The council would decide during the next few days exactly how the funds would be distributed, but the intention was to support the victims' immediate families.
The National Rural Fire Authority's Auckland region fire manager Rob Goldring urged people to give as generously as they could.
The funeral of Mr de Ridder will be held in the Bay of Islands tomorrow.