Try and find some of this
. I have used it on my 75g tank which had the same problem as yours.
Take the background off, smear that stuff all over and put it back on. Using something with a flat end and preferably rubber, start from one side of the tank and work your way across and you will find you have got rid of most of the air bubbles.
If you have a magnetic algae scrapper that works well also (just go very slowly)