I've had some of my tanks for almost 20 years old. They have always been in a working fish room so I was never much concerned about hard water stains on the tank glass until I set up this fish room with a sofa in front of the tanks. Since the tanks are as much for beauty as and breeding and grow out space the hard water stains really bothered me and nothing would get them off. I used CLR and even acidic toilet bowl cleaner which worked better than the CLR but not well enough. Last week I bought cleaning vinegar at the dollar store. A half gallon of the stuff was less that $2. I gave it a try and now the outside of my tanks are crystal clear. From now on, when I have an empty tank I will use it on both the inside and out side of the glass. I put it in a spray bottle and use it like I would use Windex. Try it. You'll like it.
