Most new turtle owners are surprised to learn how involved it can be to assemble a habitat that suits a turtle's needs for health, safety, and well-being. Such a project can also be very expensive if approached from an uninformed perspective. Here you will find the basic elements in creating an adequate habitat for your turtle, and we will hopefully address your concerns regarding financing, space, maintenance, and aesthetics.
The first thing to consider is your turtle's tank, but not just any tank. You need a tank that's big enough to hold a turtle! Turtles create a lot of waste, and they need to have enough water to dilute the waste as it is being filtered. Without lots of water, the toxins will build up and can have harmful effects on your turtle's health. Additionally, turtles love to swim in deep water. They need enough room to dive, chase down fish, and play. They are territorial animals and need to have enough space to call their own.
There are two ways to determine tank size. The first is the 10-gallon-per-inch rule that bases the measurement on the volume of water, and the second is the 4X-2X-2X rule that bases the measurement on the tank shape.
10 gallons per inch
A turtle tank needs to hold 10 gallons per inch of turtle, plus 15% extra space for basking areas. For example, a female RES will be 10-12 inches when full grown, so they will need a 140 gallon tank filled with 120 gallons of water. This rule is good to use for tanks that may have a more unusual shape.
Use "X" as the turtle's maximum size. The turtle tank should be 4X by 2X by 2X. For example, assume a female will grow to 12 inches. She will need a tank that is 48 inches by 24 inches by 24 inches. This is actually a standard glass tank size for a 120 gallon tall tank.
Turtles are territorial and often can not share space. If you have multiple turtles, add all their sizes together and add in an extra 30%. If you have two female RES (who will each be 10-12 inches!), and you are using the 10-gallons-per-inch rule, you will need 280 gallons PLUS another 30%! Two female RES should be housed in at least a 350 gallon tank. Even then, there's no guarantee that they won't fight. For this reason, we recommend either separating turtles or building a large pond.
There's lots of types of tanks to choose from, so don't just buy the first tank you see!
The most popular choice among turtle owners is the classic glass tank. It looks very nice in a home, and it can be special ordered in multiple sizes or even custom designed for your home. A glass tank can be very expensive though.
A less expensive option is a stock tank. Stock tanks are large, heavy, plastic tanks designed for industrial and farm use. You can find them at farm supply stores and can special order them at home improvement stores. A stock tank will cost about 1/4 the price of an equivalently sized glass tank. Considering how many other costs there are (filtering, lighting, heating), this is appealing for many turtle owners. A stock tank may not be as attractive as a glass tank, but can be modified to look like an indoor pond. If you do not want to invest in a glass tank, but you still need something that looks nice, you can solve the problem with a little creativity. Some people drape fabric around the outside to hide the tank, filter, and cords. Others have built wood cases around their tanks and stained them to coordinate with the furniture. A stock tank can also be painted with non-toxic paint as long as not paint will be exposed to the water.
Ponds are a great option for anyone with a permanent home and multiple turtles. A well tended pond can be custom designed for your yard and may increase the value of your home. If you do the labor yourself, the price is not much over a stock tank.
Avoid acrylic tanks for turtles. The acrylic will quickly become scratched by your turtle's sharp claws. Within a few months, it may be so scratched you can't see into it.