this is a common problem for boat owners - the diesel is less refined than car diesel, boats get left for long periods without use - especially yachts (at least longer than most cars) and the environment is quite damp(!)

There are a number of chemical treatments available that can kill and breakdown the algae allowing it to be burnt - I suggest you find a local(ish) yacht chandler and have a word with them - I can suggest the chemicals I use, but I am in the UK so I think this will not be useful to you

treat the tank - and use the car then feed it fresh fuel (and treat that) a couple of time and I expect it'll be fine.