Glass that never gets foggy?

Ok... It's more like a spot on it. I've had my aquarium for a few years now. Anyone that has one knows about the algae microfilm and calcium that deposits or grows (coralline) on the glass.
I have scrapped my glass thoroughly with blades, I have used a scoffing, non abrasive pad and I have used my mag float to take care of the view restricting films that grow there.
The thing is... That for 2 years now, there is a perfect circle on the inside of the front glass made by the suction cup from a seaweed clip where the foggy film does not stick. Even if I clean the whole front glass with equal effort all across, that one round little spot looks perfectly clear compared to the rest of the glass. That one spot looks like there's a hole through which u can see in high def compared to the rest of the glass!

Does anyone know how I can make all my glass look like that?

Like I said, I scraped with blade, scrubbed with pads used mag float... I'm determined to make it all look like new and I need your advice and experience. Tank is full of water and partially stocked.

Picture of the spot is bellow. I haven't cleaned the glass in a few days so u can see. My clown, who likes to keep protagonism is posing right in the center of the so called "hi def" spot. Thanks in advanced.

- Milton.

 

That's odd. I really don't know. Hopefully someone else will chime in. Crazy!

 

I know... I'm really curious about this. One of my possible theories is that the suction cup from the clip had some kind of silicone film that stayed on the glass... But again... that is just a theory.

Please, 3reefers, share your cleaning secrets with me when it comes to cleaning the inside of the glass!

 

My tank I kept African cichlids in (very hard water) was a cheap tank and developed the film you speak of. I'm interested in hearing more info too as I could never get it clean and plan on getting rid of it for this reason.
Its almost like the glass absorbed calcium into it.

 

I imaging there are microscopic pits in the glass where bio-film vs carbonates eventually take hold. Since the surface is pitted microscopically any instrument that cleans the glass can not get into those areas.

 

At a microscopycal level the bio-film May not b as noticeable, but why is that one area still not affected by the opacity?

I'm tempted on my next water change to get a bit of sulfuric acid in a rag and rub around that spot to see if it will all clean like that.

 

Glass can be become subject to corrosion here is a site http://corrosion-doctors.org/Household/Glass.htm
More like errosion but still we are putting alkali in our tanks so thats the only thing I can truly think pf

 

Wow! Thanks for the link, skyvern2130.
So according to that info, eventually my aquarium glass that is constantly attacked by my alkalinity additive will get thin and eventually break.... That will not happen in my lifetime, thank God... But that may very well be the reason of my "foggy" glass.

Anyone care to share the techniques that better work for you when cleaning the inside of your aquariums?