why do you suspect algae? was the tank full to top? I just went through awful agae problem. Use see thru primary fuel filter and look for scum to build up when tank gets low. If you get algae in filter then drain tank, take it out (very easy to do) and take it in to have it flushed (costs about 50 bucks). this will save you a lot of trouble....make sure you remove the tank screen when you take it in the idiot that did my tank didn't do so (even after I warned him) and it disappeared (he replaced it for free btw).
good luck