Hard dot green algae on glass

[examiner]

My BB tank has been up and running about a year, I just can't seem to eliminate this algae from my glass. I don't get much of a film (clean glass about 1x week), but these darn little dots keep popping up everywhere.

With the exception of bubble algae, the tank is nuisance algae free. Nitrates are undetecable, phosphate is .02 with a Hanna meter. All my other parameters are "within guidelines". I have a ASM G3 on a 58g tank so I skim pretty aggresively. Corals exhibit good growth and improving color.

I just don't remember being plagued by this on my old DSB tanks. But maybe that's just a fond mis-recollection clouded by advancing years.....

Any advice?

(btw, great new forum! Been visiting a while, but I think this is my first active participation)

[SeanT]

Is this algae easily removed by the pad on your finger or does it need to be scraped off?
Also, do you siphon regularly or let detritus build up?

Thanks,
Sean

[examiner]

Thanks Sean. No, it's hard. Not quite coralline hard/razor blade required hard, but hard nonetheless. If I'm using something like a mag float to clean the glass, the inner part of these "dots" comes off pretty easily, but the outer ring requires repeated furious scrubbing to eliminate.

I siphon weekly during water changes (10%), clean the sump monthly, turkey baste the rocks a few times a week If I piled a weekly collection of detrius up, it would amount to about a half dollar sized pile. 3 small fish in a 58g, but my cleanup crew is lacking (probably only about 6 snails at present).

[concept3]

examiner-

my brain could be playing tricks on me, but i had something rather similar happen to me about a year ago. I got this coralline-like green dots on one of the sides of my tank on the glass, and I gave up on scraping it off. Within about a month or two (with weekly dosing of B-ionic and daily Kalk water), it started turning into purple, and eventually changed from green to pink/purple dots that looked like coralline. Now the tank is all purple of course. I do remember at the time, I had just switched my PC's for AB 10K (13K on box) halides- could this be a growth of pre-coralline algae?

[examiner]

It could very well be some type of coralline, I know purple isn't the only color it comes in. I do have a minor plague of purple corraline on the glass that I need to attack vigorously with a blade every month or so. It's not a big deal, and I'm certain it's not related to any water quality problem, so I suppose I'll just live with it, see if it runs its' course (as so many other things do in this hobby).