I am using a 32g Brute Trash can to mix my saltwater but without any markings, it is hard to get a precise water volume for when I only need to make 15g as apposed to 32g. Now, I understand I could just use half the can and call it good but I prefer to be more specific with it. Since I am using the grey can, I cannot see the water volume from the outside. What are some ways I could leave marks in the tank to show when I have 10g, 20g, 30g, etc.? I was considering just using a Sharpie but would prefer to not have outside chemicals in the bin.


