Completely light free storage helps a ton.
The plastic tanks in pickups are slightly translucent allowing sunlight in and promote the growth. Old school metal tanks block the sunlight and don’t allow growth. Thats why it doesn’t grow in the tanks at fuel stations. Some tanks are now being done with fully sealed fill caps to ensure no sunlight penitrates and the vent lines are being built with off sets to block all uv light travel.
I have been contemplating making a new main fuel tank from fear of bugs. But since almost no one in Southern Nevada has the problem, I don’t bother.
The other common err in fuel storage is being sealed. You want it air tight. The lighter molecules will off gas and escape. No one want the gurgle of the drinking water bottle effect, however that is better for never allowing the vapors to escape.
Depending how large a storage tank and how long it is stored becomes the question of cost vs reward.
In the pickup if you store fuel a long time, yes a 100% full tank is best. On the no uv light issue, maybe painting the tank black is worth while. Vented fuel caps have their place, but unless your tank and fill line has no room for expansion- and your truck is stored where temperature fluctuations are big enough to cause swelling and shrinking of the tank- get the sealed cap on there for storage and just put the center cap in a ziplock baggie on the driver’s seat so when it’s time to revive, it isn’t forgotten.
Btw, a finger tip wipe of oil on fuel cap o rings extends their life a lot. Many classic cars in storage people simply spray wd40 on all the rubber parts like the hoses, belts, tires, etc. it soaks in slowly and forms a barrier that slows the outgassing of the hydrocarbons.
