Agree. Use a credit card first. Calcium deposits are quite hard. Another option is to use a good magnet glass cleaner with a metal blade.
I try not to use blades with hands directly as there could be uneven/excessive pressure -> risk of scratching the glass.
Using the blade mounted on a magnet cleaner ensures 'even & just sufficient pressure' (eg. DD Ocean or Tunze are brands i've used)
Hi Bro Daveyy, Its been awhile, so glad to see you still active.
Here is my FTS.... I started keeping whales!
Just kidding bro... me still as 'kah-jiao' as always! Will take a proper shot one of these days before posting. Hope your tank doing well.