Algae and new tanks

My LFS told me to just go ahead and use tap water for my start up, so
I did. Said that RO gave too many headaches in terms of balancing.
Now, algae is rampant. I guess that's a good thing from the
standpoint that my tank supports life. :-)

Just two and a half weeks into cycle, I have stopped using the Purple
Up that was recommended to me by my LFS and LS/LR dealer (I got it
mail order). It seemed to be driving my pH way down... I dunno.

So, right now,
ph is 8.2
NH3 - 0
NO2 - 0
NO3 - 100
sp gr - 1.023
water temp between 81-88! Yikes! Ambient air at 77 day, 74 night.

I am hoping that the algae will eat up all of the free nitrogen like
it does in my garden. The LFS guy also swears that the algal bloom is
also an inevitability.

Thoughts? opinions?
Thanks,
Dave in Simi Valley