My water hose was left on for a whole night (by accident) and our bill was only like $5 more.I have a 20 gallon that I do 25% weekly water changes on and it uses way less water than my showers every month.It's like 25 gallons a month thats like 1 bath I doubt it's $30 lol.I'm not suggesting you argue with your mom and get in trouble but I would ask her to prove how it cost that much money a month for your water changes.I give my mom and dad $10 a month for the water and electricity my tanks use but they tell me I don't have to so it can't be costing that much.Since they make me pay for everything else lol don't turn 16.ever.