Trying to head it off

[ADMWNDSR83]

So... My shell dweller tank has been running with the little ones in it for several weeks now, and I'm starting to see some green algae on the shells, especially, and maybe two small spots forming on the back wall.  I'm not against the natural look, and as long as the front wall stays clear I don't have a problem if the back gets funky, but I want to make sure I am keeping an eye on it so it doesn't get out of hand.  I do have about 8 trumpet snails crawling around in there as well.  

Basically, I am wondering if this is going to be ok, and just let it go, or if I should think action steps.  Part of my deal is that all of my other tanks are heavily planted, so this one, with no plants at all, scares me.  Thanks for any insight.

[xXInkedPhoenixX]

If you don't want it to go too far why not just scrape the glass with a razor and follow behind with a siphon if possible? I'm sure you probably have to leave the shells alone but they might look cool. 

[Guppysnail]

It could be green spot algae. Api makes a phosphate test. My understanding which is not the best when it comes to nutrients causes of specific algae is lack of phosphate is what causes green spot algae.