BOM so far
TDS sensor $22
https://www.ebay.com/itm/123893336802

DS18B20 temp sensor $4
https://www.ebay.com/itm/262081155631

PH sensor $7
https://www.ebay.com/itm/112650779679


float switch $2
https://www.ebay.com/itm/332899270530

peristaltic pump (dosing nutrients into reservoir) $13/ea
https://www.ebay.com/itm/163276942489

submersible pump (circulating nutrients) $5
https://www.ebay.com/itm/282826414357


existing stock
raspberry pi 1 model b
5v power supply (old phone charger + scissors/wirestrippers/...)
5 gallon food grade buckets, free uncleaned from nearby food processor
mosfets for driving large dc loads from microcontroller pins. 

TBD
perlite, plumbing and other hardware store stuff


current status: working on drivers/firmware adapters for sensors, kinda low motivation, not sure if any reason to continue online documentation?