Pls check pics...what do you make of this?

[lazarus]

You may have seen my thread..."what have i gotten myself into?"
well your advice has been great...nearly all problems solved. but my sand is looking green and mostly purple under the surface, and i just cannot seem to get the refugium jumpstarted. Tank is only 2 mos old. 115 g. FOWLR about 1200 gph flow. 82 F (hey its summer), and all other parameters are cool.
Pls check out my pics and let me know if this looks like an accident waiting to happen.

 

[murph]

Looks like cyano growth to me. Common for young tanks. For the growth on the front of the tank below the surface of the sand bed you could just cut off its light supply which will probably cure the problem.
Take some duct tape and run it across the front of the tank at about the height of your sand bed to cut off any ambient light coming from the room/window. Ya; I know its going to look ugly for awhile but I be it will do the trick. Just make sure you have cut off all its light. Might take two or three layers of tape depending on its thickness.

 

[lazarus]

thats a terrific idea and i did it...but now i see the duct tape left behind a residue.
whats the safest way to take this off acrylic?

 

[my way]

There are citrus bases glue removers, I don't know brand names off hand though, wd40 sprayed on a rag will work also. just spray the rag in another room.