It's removeable...
Everything on a boat is removable. Some things can be removed easily...others involve varying degrees of surgery from minor to major to just short of taking the boat completely apart...but everything CAN be removed--and usually put back together a lot more sensibly than the builder did it.If you know that the tank is full of white flecks, you apparently have access to the inside of it. First, find out what the white flecks are. If they're mineral deposits, you may be able to dissolve them with a strong solution of white vinegar. If not, put enough water in the tank to suspend them and use a shop vac to remove them. However, unless they're clogging up your water pump or causing other problems in your plumbing, I'd wait till the season is over to do anything. It's just too d'd HOT to take on ANY project you don't absolutely have to do right now!