Hard water

For us poor mortals "darn sowf" we have very hard water, which when evaporates leaves nasty chalky lines on the glass.

My main tanks look fine probably because they have hoods and strips across the top to disguise this, but I have a little desk top tank that has lovely rounded corners and led lighting, I'm sure you guys know what I mean, it just has a beta and some cherry shrimps, but the "tide marks" at the top don't look attractive.

Does anyone have a good method of removing these without scratching the glass or upsetting the inhabitants??

Thanks
Lindsey

Sorry I can't help as I have to deal with lovely soft water
Lisa