Apartment internet bandwidth monitoring?

Hi all,

A client who is supplying internet connectivity to an apartment building would like the ability to track bandwidth usage to see top users. A Juniper SRX550 is supplying the clients DHCP on a public /23. Switch’s are all Juniper EX2200.

Could I please have some recommendations for free or low-cost software for this? I have previously used Solarwinds and LibreNMS for network monitoring but don’t think they will do the trick here.

Thank you for any suggestions!