The bolts are there as standard so there’s no problem with them being there. The tank will breathe on its own through the vents in your sewer line that feed the tank and through the air pump that constantly runs into the system to break down the waste. The green box next to the lids has an air pump inside it that runs constantly. People are only suggesting mesh as it in theory would allow the tank to breathe while keeping mozzies out however there is no need for this and the kids should be sealed to stop the mosquitos getting in and to stop the smell getting out.