i personally would never use distilled water in the first place. you can buy ro water from walmart and abunch of other places for cheap. but there are also alot of very decently priced rodi units on the market right now.
now for your question. i think we would need to see some pictures of the algea to ID it, but from how you describe it the algea sounds like cyano wich in fact is not really an algea but a bacteria. there are acouple of different things i have seen eat the stuff but it is kinda hit or miss from what i have read in the past. some conchs that i have had have ate the stuff. 1 was a crown conch, burrowing conch and both of these i had bought from that fish place. the others were just common rock urchins that are sold just about anywhere that sells aquacultered live rock. they usualy come in on the rocks as hitch hikers.
there are upsides and down sides to all of these inverts. all of them are clumsy and like to knock things over that are in there way, the urchins of course like to eat coraline algea and will slowly over time eat apart your rocks. the conchs need a fairly deep sand bed.
now again these are hit or miss here. i do recomend trying to fix this problem though. there is always a reason you will have cyano or any other algea. if you do not fix the problem you will never actually get rid of the stuff. there are many different reasons you could have the problem and the most comon i would say are too much nutrients in the water, old lights, not enough flow or over feeding. i hope this helps you out some.
