What is a good diesel fuel additive

[Chris]

The 83 FC35 I purchased had set for some time with a full 265 of diesel
fuel. Should I use any kind of additive to kill any possible algea or
other contaminate? I replaced the Racor filter and I am still trying to
get the filter on the engine off. I have noticed alot more pick up
since the Racor change. I have been driving once a week about 20 miles
and all seems ok. Sometimes it is a little hard to start though. My
manual says not to hold the starter for more than 30 seconds..Is it
common to take up to 30 seconds to crank? The most I have had to hold
it is anywhere from right away to maybe 7 seconds...
Also, any recomendations for a coolant additive? I am not using the CAT
coolant at this time.
Thanks
Chris Reed
83 FC35 SB
Plant City, FL.