Rainwater Harvesting in repurposed 500 gallon diesel tank

I can get my paws on an old 500 gallon diesel tank. Is there any way to clean the diesel tank so residue from the old diesel fuel won't kill my plants or fish

I assume there's not a big lid that can be removed. A trick used on old gas tanks in cars is to put water and sand in it and roll or shake it to scrub the inside.

I've got a standard IBC(tote tank) that used to hold diesel; the inside is pretty nasty, not just stained from diesel but near the bottom appears coated with contaminants. I can't tell you a way that works well, but I can tell you that trying to clean it off with an air compressor is not very effective, and scraping/scrubbing through the small top opening really sucks... at least the air compressor was good for blowing the loose bits out the drain.

So far I've got the easier half of the gunk off. Maybe following Wayne's suggestion would work if I took it offroading while partially full of sandy water; can't really see any practical way to shake a tank that size without mechanical assistance.