The treasurer shall be required to give a bond or evidence of equivalent insurance of not less than one hundred fifty thousand dollars or he or she may be required to give a bond or evidence of equivalent insurance double the sum of money estimated by the council to be at any time in his or her hands belonging to the city and school districts, and he or she shall be the custodian of all money belonging to the city and all securities belonging or to be held by the city. He or she shall keep a separate account of each fund or appropriation and debits and credits belonging thereto. He or she shall give every person paying money into the treasury a receipt therefor, specifying the date of payment and on what account paid, and he or she shall also file copies of receipts with his or her monthly report. He or she shall monthly and as often as required render to the city council an account under oath showing the state of the treasury at that date, the amount of money remaining in each fund, the amount paid therefrom, and the balance of money in the treasury. He or she shall also accompany such accounts with a statement of all receipts and disbursements, together with all warrants redeemed and paid by him or her, which warrants, together with any and all vouchers held by him or her, shall be filed in the clerk's office, and if he or she neglects or fails for thirty days from the end of any month to enter such accounts, his or her office may by resolution of the mayor and council be declared vacant, and the mayor with the concurrence of the council shall fill the vacancy by appointment until the next election of the city officers. The treasurer may employ and appoint a deputy and an assistant or assistants as determined by ordinance. The treasurer shall be liable upon his or her official bond for the acts of such appointees.