need help with the removal of calcium buildup

Calcium deposits on hoods, lights ect.
I just took a ride last night to womans house i found on craigslist. She GAVE me 5 tanks all together four ten gallons and a fifteen gallon, three stands, and two boxes full of filters, heaters and other equipment. Most of the tanks had hoods and lights with them. The tanks have all cleaned up pretty well but the hoods are all covered in the white stains. I have tried vinegar and lemon juice with little to no success. What have you guys used that has really worked. It was all free so maybe i should spring for new hoods, but they are in good shape except for the stains.
thanks

 

cut a lemon in half, pour table salt onto it and start scrubbing, if they are glass it shouldnt scratch, if its acrylic Id be weary.

 

Tried the juice with the sald.....another dud, the tanks are clear as a bell, but i cant seem to get it off the hoods, ill try the real lemon tomm.
Thanks

 

O off the hoods, youll have to use something with more friction. If its just the black plastic hoods try steel wool

 

I use Magic Erasers and a straight edged razor blade. Scrape and then scrub. If they are acrylic though I wouldn't use this method. With glass I haven't had any scratches or any problems. Just be sure to wash really well after using the magic erasers.

 

If you use a razor blade make sure its (a) brand new/extremely sharp and (b) only scrape with the blade at an acute angle <45 degrees to drastically reduce the risk of scratching the glass.

 

Thanks uncw.. I didn't even think about adding that, I use them on my porcelain stove top all the time and it is just such a habit I didn't think to clarify the angles..