pg_activity

pg_activity is the best I can find to monitor PostgreSQL database generally. pg_activity on GitHub

Install pg_activity

sudo apt install pg-activity

Use pg_activity

sudo -u postgres pg_activity -U postgres

Compile from source (optional)

sudo apt install python-setuptools libpq-dev build-essential python-dev
cd /tmp && git clone https://github.com/julmon/pg_activity.git && cd pg_activity/ && sudo python setup.py install