Calculate the minimum recommended tank size for your turtle using the industry-standard 10 gallons per inch of shell rule.
For each inch of shell (carapace) length, provide at least 10 gallons of water. A 6-inch slider needs a minimum 60-gallon tank. Each additional turtle requires roughly 50% more space to reduce stress and territorial fighting.
Turtles need swimming length more than depth. Aim for a tank at least 4× the shell length long and 2× wide. Water depth should be at least 1.5× the shell length so the turtle can flip itself upright if overturned.