Help with clowdy/dirty glass

[TexAgReefer]

I recently bought a used tank. Overall it looks great but there is something on the glass on the inside that I can't seem to get rid of. While not a major nuisance and most people wouldn't notice it, it does take away from the clarity of the glass.

It looks like water spots/staining. I've tried scrubbing and a razor blade with no success. The tank is filled and running with livestock.

Unfortunately it is virtually impossible for me to get a clear picture

1) Any idea what it is?
2) Any ideas on how to clean it?

 

[KrisReef]

Probably calcium deposits. Vinegar may help

 

[AllSignsPointToFish]

It's probably calcium buildup...a very common occurrence in used tanks that have been in high hardness/alkalinity service.

I circulated acidic water through my used tank which knocked down the cloudy spots...along with scraping.

I can still see those spots when the water level is low during maintenance or water changes. I'm not sure there is much you can do in a tank that is running.

If if were calcium deposits in a pool, lowering hardness with sodium bisulfite would eventually remove the deposits.

Sorry I can't be more help!