Aquarium Glass

[AngelLover]

I have a 29 gal hex -- at least 10 yrs old.  The glass seems to have developed a film - possibly mineral?  It is not at the waterline, but the entire depth of the glass.  I have tried unsuccessfully to clean this.  My pleco does a much better job -- glass now has clean specks where he has grazed.  Now the question is, is he mechanically cleaning it by scraping or dissolving any film on the glass as he feeds?  I'm sure in time, he'll have cleaned the majority of it, but it will take forever.  Meanwhile - the tank looks terrible.

Has anyone come across something like this before?  Any solutions other than dumping the tank for a REAL cleaning?  

 

[AngelLover]

... uh oh.  Not much of a pleco expert - this boy was a return to the fish store.  I felt sorry for the big lug - approx. 4+".  Looks like I'll be looking at some pleco pix to try to identify.  No mechanical scrubbing I've done so far seems to make a dent in this.  That's why I thought it might be a mineral build-up of some sort ... kind of annealed itself to the glass.  Might try some really fine plain steel wool on my scrubber.  Can you tell I'm getting desperate?  The water is really clear - you lose the affect with the mottled viewing surface.  
Based on the pix in my Alexrod's Mini-Atlas -- closest match is a Peckoltia brevis.  This fish is not very cooperative .. not leaving the luxurious hollow he has dug under the driftwood for a good view.  I can see smooth snout -- no bristles.  Don't remember seeing anything tooth-like the one time I saw him hanging on the glass.

 

[Lilpoot]

What kind of Pleco is he?  Some species actually scour the surface they are sucking on with sharp tiny little teeth.  Others just have more rubbery teeth that wear down the stuff they are sucking on.