NO! Update - tank and fuel system cleaned out. Waiting for new fuel filter and hope to have it running up this week. Thanks for the input everyone.
Algae does not grow in fuel, it needs sunlight. You have that mistaken for microbial growth which happens in biodiesel and is worse with more water present, and when it sits for long periods. It can be treated with a biocide, but it's best to clean everything out. It sounds like what he had was a big glycerin dropout, which is from biodiesel. There may have been microbial growth as well but it's hard to tell from the description. Biodiesel has many problems and storage is just one of them. If you have any equipment with a blend of bio, run it out before storing. The good news is that old engine can handle a lot of crap fuel without wrecking your injectors, but try running bad fuel through tier 3 and 4 high pressure common rail diesels which are up to 45,000psi at injectors and you are in for some expensive nightmares.
Update: got hit by old man winter yesterday and used the blue beast cleaning ice/snow off Mom's driveway. This would've made my Dad happy.
Nice tractor. I've got a Ford 2120. 43horse 4 cyl diesel 4 wd. The thing is indestructible, and I've tried!