I use PRI-D diesel stabilizer on all my diesel holding tanks and fuel tanks, it prevents even rust in metal tanks, I purchase about 1 gal of PRI-D every two years, 1 gal treats over 2000 gallons, if you treat the fuel in the holding tank once a year you can keep the fuel stable for years I'm talking 8 to 10 years. the same for gasoline except using PRI-G, it has been tested that it keeps gasoline stable for 12 years if treated once a year.
1 gal of PRI-D (diesel) is $80 treating over 2000 gallons, 32oz of PRI-G is $33 treating over 500 gallons, the PRI-D also works good for kerosene/aviation fuel. The PRI products is Military/NATO approved that far far exceeding Sta-Bil