Just be aware, dryer cords and outlets are generally 3 wire devices. They deliver 240V and ground - No neutral....
I want to build the control box and put in the elements all at once.
Having a 220v 30a GFCI outlet in place the remaining parts are the following:
4500W Heating Elements (2)
PID - $45 from auberins.com
SSR - $10 on ebay
dryer cord - $10 at home depot
dryer receptacle - $5 at home depot
temp probe - $20 on ebay
box to put it all in - $15 at lowes
power switch and receptacle for pump - $7 at home depot
power switch for turning element on and off - maybe $10 at home depot
...