My 2002 37' patriot is having algae buildup in the fuel tank.  Has anyone had this problem and if so, how do you fix?

You can kill the algae with a good diesel biocide but the matter will clog fuel filters.

You can have the fuel "polished" or cleaned to get rid of the residue. A boat marina can direct you someone who can do it.  They usually do it through the fuel fill spout.

I was told by a large truck repair shop to never use a biocide....  He told me that major problems can occur in the engine after using this kind of product.  I will try to find someone that can clean the fuel in the tank.

Karl,

I would consider talking with the engine manufacturers marine division. They must have a course of action to handle this problem as a routine. It is not an uncommon problem in boats. Someone can scrub the existing fuel but without some form of biocide it will likely be impossible to eliminate the source of the growth. My guess is that they will want you to get the fuel scrubbed to remove the bulk of the problem and then kill the rest with biocide with some additional fuel filter changes as part of the procedure.

Later Ed

Of course the reason for algae growth is the presence of water in the fuel tank or possibley a bad load of fuel.  I suggest so sort of pump with a filter to circulate the fuel from one side to the other(fuel doors)
Then apply a small amount of biocide should do the job.  If not then drain the tank mine has a plug in the front and re fuel.  I worked for Caterpillar Truck Engine Division for over 15 years and I do not believe other than frequent fuel filter changes that the fuel now in the tank would harm the engine as long as you change the filters often.  The only risk would be a plugged filter at the most inconvienent time.
Also, there are treatments for this problem sold at truck stops.  The only reason that the engine manufacturer does not endorse the product is for liability reasons. Sorry for the long response. Hope this helps.

Karl
If you go to the website For Power Research inc, They are located in Texas.
I have had great results using their product in RVs w/Aqua-Hots Systems.
Thanks
Orman