Best Turtle Tank: Size Calculator and Buying Guide

One owner on r/turtles read that 20 gallons would do for a razorback musk turtle and bought a 40 gallon breeder tank instead. Years later the turtle was using the whole tank and still looking for more room to swim. The owner moved up to a 60 gallon breeder and reports a more relaxed turtle that no longer flails at the glass.

The rule below puts a full-size razorback higher still, at about 69 gallons of water. The best turtle tank is one sized for the adult turtle, because aquatic turtles live 20 to 40 years or more and a tank bought for a small turtle does not stay big enough for long.

The rule: give your turtle 10 gallons of water for every inch of adult shell, then check how much water the tank really holds. A 12-inch female red-eared slider needs 120 gallons of water, and that takes a 150 gallon tank once you leave room at the top. Pick your turtle below to get the size for yours.

This calculator covers aquatic turtles, the kinds that live in water and climb out to bask. Box turtles and tortoises need a land enclosure, so these numbers do not apply to them.

Best turtle tank by situation

Once you know how much water your turtle needs, the choice comes down to a few tanks. These four cover most adult turtles. Glass gives you a side view. A stock tank, the big plastic tub made for farm animals, is wider and has a drain plug.

Find the best turtle tank for your space

Six questions narrow the list by water, view, gear, room, draining and budget. The calculator above can fill in the first answer for you.

The gallons on the box are not the water inside

Type “turtle tank amazon” into a search bar and you will see 50, 60 and 67 gallons in the titles. Those numbers can be far from the water the tank holds. Several tanks sold for turtles have a shallow base with an open frame on top, and the gallon figure counts the air.

Tank	Number in the name	Water it holds	Water depth
REPTIZOO 50 gallon turtle tank	50	About 20 gallons	7 in
REPTIZOO 67 gallon turtle tank	67	About 26 gallons	7 in
Zilla QuickBuild turtle tank	60 in the title, 26 in the specs	About 26 gallons	About 8.5 in
Tetra 20 gallon turtle kit	20	About 17 gallons	About 8 in

Regular tanks lose water too. You cannot fill a turtle tank to the rim, because MedVet says it needs several inches of air space to stop escapes. Aqueon’s size chart puts a 75 gallon tank at 48 1/2 by 18 1/2 by 21 1/8 inches. With the water 4 inches below the rim, it holds about 66 gallons. The calculator plans on 85 percent of the labeled size, so a 100 gallon stock tank counts as 85 gallons of water. To work out the water in a tank you already own, use our aquarium calculator.

Depth matters as much as gallons. VCA recommends water at least 1.5 times the shell length and a swimming area at least 4 times the shell length. A 7-inch base gives a 10-inch slider far too little depth.

Musk turtles are bottom walkers, so they need a way up. One r/turtle owner ran a 75 gallon half full, then filled it to the top and saw a musk turtle struggle to find the ramp. Replies on the thread disagreed about the drowning risk. The owner added a large rock so the turtle could reach the surface, and it later learned to use the platform.

Glass aquarium or stock tank

This is the biggest choice after size, and it comes down to whether you want to watch your turtle from the side.

The best aquarium for turtles is long and wide, and glass gives you the view, but big glass tanks tend to be narrow. A 125 gallon is about 6 feet long and 18 inches wide. One r/Aquariums owner upgrading from a 40 breeder could fit only a 4 foot 75 gallon, because a 6 foot tank missed the wall by 2 inches. Measure the wall before you choose. Glass also has to sit on a stand made for it.

A stock tank is wider and sits on the floor. One r/turtle owner who bought a 150 gallon Rubbermaid tub says it can go on a floor, carpet, wood or concrete as long as the surface is level. Empty, a Brute 100 weighs about 32 pounds, and an Aqueon 75 weighs 98. Brute tanks also have a drain plug, so a hose does most of the water change.

The trade-offs show up after setup. An owner of two 300 gallon outdoor Rubbermaid tanks says the turtles have plenty of room but are seen less than in glass. One owner who moved a turtle from glass to a 150 gallon stock tank saw it slide off the dock and rarely bask there. A commenter on r/turtles adds that steep sides and one water depth leave few places to rest. Test the dock and ramp before the turtle moves in.

Bare tanks have one more problem. An owner of a 300 gallon stock tank with three turtles says it rusted a bit and the turtles wore down their nails until they struggled to climb onto the platform, and advises a pond liner. Rust is a problem for metal tanks. The Rubbermaid tubs in this guide are plastic.

Buy for the adult turtle, not the one you have today

A small turtle in a large tank is fine. VCA says it is better to start juveniles in a large tank. One r/turtle commenter says sliders outgrow 30 gallons in 2 years and bought a 150 gallon stock tank to stop upgrading. A parent on r/turtles bought a 110 gallon stock tank right after two tiny red-eared sliders came home.

One owner moved two red-eared sliders from a 55 gallon to a 125 gallon after their shells reached 8 and 7 inches. A commenter told that owner two adults would need a pond or stock tank of 300 gallons or more to share, far above the calculator’s number.

Federal law helps here. Turtles with shells under 4 inches cannot be sold as pets, so a turtle bought legally as a pet already needs about 40 gallons of water by the 10 gallon rule. A 20 gallon kit from Amazon holds less than half of that. The small tanks in this guide are for rescues and tiny turtles already in your care.

If you already have a tiny turtle, buy the largest tank you can fit. Shell length is measured in a straight line along the top from front to back. Skip the curve of the shell.

If you rent or live upstairs

One r/turtle owner put a rescued eastern painted turtle in a 75 gallon tank, then learned the apartment did not allow aquariums over 20 gallons. The owner had one month to rehome her, and the floors were the main worry: could they hold more than 1,000 pounds? The turtle went back into a 20 gallon while the owner called four rescues, zoos and reptile centers.

Read your lease before you buy. Water weighs 8.34 pounds per gallon, and a large tank is heavier than most furniture. These are Aqueon’s weights for a filled tank, before rocks and a stand:

Glass tank	Weight when full
55 gallon	625 lb
75 gallon	785 lb
90 gallon	1,050 lb
125 gallon	1,400 lb
150 gallon	1,800 lb
210 gallon	2,450 lb

A filled 75 gallon puts about 126 pounds on each square foot under it. Residential floors are commonly designed for 40 pounds per square foot across the room, so a large tank upstairs is a question for your landlord or a structural engineer.

Renters face more than the floor. One landlord asked an owner with two 75 gallon tanks and a 55 gallon for insurance that covers cracks and water damage. Stands need the same care: when one owner showed a 55 gallon turtle setup on r/Aquariums, a top reply said to drain it unless the stand was welded steel and rated for the weight.

Plan the move as well. One family drove 4 hours to collect a 180 gallon tank for a turtle, and a strap slipped on the last stair and cracked one side. Most replies said replacing a pane means rebuilding the whole tank, so buy glass close to home if you can, and move it empty.

If you keep more than one turtle

Plan on one turtle per tank. The Merck Veterinary Manual says aquatic turtles are best kept as single pets, and PetMD says never to mix species and warns that males fight.

Two turtles that get along can still turn on each other. One r/turtles owner kept two female red-eared sliders for more than 13 years, through 20, 40 and 100 gallon tanks. Then they started fighting. Separate tanks stopped it, but the two still cannot be out together: the smaller one chases the larger and bites her feet. Another owner saw attacks start after years of calm between an 11-year-old male and a 9-year-old female, in a tank the owner calls a bit small. A third took a male to the vet for neck wounds after more than a decade together.

If you keep two anyway, the calculator adds 50 percent more water for each extra turtle, the figure ReptiFiles uses. Sources disagree: Florida’s caging rule adds 10 percent to floor and pool area, and PetMD adds 25 percent to each dimension, which comes close to double the volume. Budget for a second tank too, because you may need it on short notice.

What goes with a turtle tank

Only the kits include gear. Every bare tank here needs a filter, a basking dock, a heat lamp, a UVB lamp and usually a water heater. Check that the dock is large enough for the turtle to climb fully out of the water. VCA’s guide puts the dry area at 15 to 25 percent of the water surface.

The filter needs the most attention, and it should be sized for the water. ReptiFiles says to use a filter rated for at least twice your water volume. One r/turtle owner moved from a 20 gallon to a 55 gallon with a Fluval 207 and saw floating waste within hours of each water change. Replies said the filter was too small, and the tank did much better with a Fluval 407. Another owner left a 40 gallon and a poor filter for a 75 gallon with a canister filter and reports clear water, with 10 gallons changed each week.

Bigger is not always safer in a small turtle’s tank. A first-time owner put a filter sized for 55 to 150 gallons on a 40 gallon, and the current flipped the hatchling. One commenter on that thread uses a spray bar on a 75 gallon, which spreads the flow.

Read the warranty before you buy. One owner with an 80 gallon stock tank lost two Fluval FX2 impellers in less than a year and says the maker’s support team told them it does not recommend its filters with turtles.

Our picks in detail

The cards list the water each tank holds, and that number is the one to shop by. Tanks are grouped by the shell size they fit under the 10 gallon rule.

For adult sliders, cooters and other large turtles

A 100 gallon stock tank fits a turtle up to about 8.5 inches, which covers male red-eared sliders and most eastern painted turtles. The 150 gallon sizes hold about 128 gallons and fit a 12-inch female slider. The 300 gallon suits a very large turtle or an outdoor pond.

For turtles up to about 6 inches

The two 47 gallon tanks fit a shell up to about 4.5 inches, which covers a male mud turtle. The Landen 120P fits a shell up to about 6 inches, which covers common musk, spotted and southern painted turtles.

First tanks for turtles under 3 inches

No adult turtle in this guide fits these tanks under the 10 gallon rule. They suit a tiny rescue or a hospital tank, and you will still need a larger tank later.

Turtle tanks compared

Turtle tank size by species

The table lists each species’ adult shell size and the tank for one male or one female.

Best turtle tank reddit threads: what owners say

One r/turtle commenter stopped buying “slightly larger tanks” and went straight to 150 gallons. Another warns that plastic box tanks sold online are too small and shallow, even for a baby turtle. A third says praise on an Amazon listing says little about whether a kit suits a turtle. One more says a 55 gallon slider tank was a wreck until a Fluval FX6 went on it.

How we chose

We started with what veterinary sources say about water, depth and length: VCA, PetMD, MedVet and the Animal Medical Center of New York. We read what owners wrote on Reddit and link each story to its source.

We compared listings for water held, depth, length, width and what is in the box, and checked them on Amazon on November 6, 2026. Where a listing gave no water figure, we worked it out from the tank’s size and marked it “about.” We did not run a lab test or keep turtles in these tanks. The 10 gallon rule is a planning rule rather than a law: VCA calls it a suggested minimum and the Merck figure works out closer to 17 gallons per inch. Tank width has no vet standard, so we chose a minimum of 1.5 times the shell length.

Before you bring a turtle home

Check your state first. Eleven states restrict the sale of red-eared sliders, Oregon prohibits pond sliders outright and Vermont banned their import and sale in 2025. Florida treats them as a conditional species. Rules change, so ask your state wildlife agency.

Turtles can carry Salmonella even when they look healthy. The CDC’s 2026 turtle outbreak made 24 people sick in 13 states before it closed in November, and over half were children under 5. The CDC says pet turtles are not recommended for children under 5, adults 65 and older or people with weakened immune systems. Wash your hands after touching a turtle or its water.

Never release a turtle. The US Fish and Wildlife Service says a released pet is unlikely to survive, and the red-eared slider is one of the world’s 100 worst invasive species. If you can no longer keep yours, call a reptile rescue, and start early: the apartment owner above found no quick answer.

FAQ

Is a 20 gallon tank big enough for a turtle?

Only for a very small turtle. A 20 gallon tank holds about 17 gallons of water, which fits a shell of about 1.7 inches under the 10 gallon rule. Mud and musk turtles, the smallest common pets, reach 4 to 7 inches, so they need 40 gallons of water or more as adults. Use a 20 as a first tank or a hospital tank.

Is a 40 gallon tank good for a turtle?

A 40 gallon is a good first tank. PetMD names 40 gallons as a starting size, and MedVet says a 5-inch turtle needs 40 to 55 gallons. The 10 gallon rule is stricter: with room left at the top, a 40 holds about 34 gallons of water, which covers a 3.4-inch shell. Most adult turtles need more.

Can a turtle live in a regular fish tank?

Yes. A standard glass aquarium works well, and it does not need the word turtle on the box. It should be long enough for the species, have space for a dock above the water and sit on a stand built for its full weight. A long, wide tank suits a turtle better than a tall, narrow one.

Does a turtle tank need a lid?

Not always. A tank with the water several inches below the rim and no dock near the top can stay open. Use a screen top if the dock sits high enough for the turtle to reach the rim. A screen also gives clamp lamps a place to sit.

Do turtles grow to the size of their tank?

No. A small tank does not keep a turtle small. Adult size comes mostly from species and sex, so a female red-eared slider can still reach 11 to 12 inches. Plan the tank around the adult size for your species and not around the size of the turtle today.

How often should turtle tank water be changed?

Change part of the water every week. MedVet recommends weekly partial changes and a full change each month, and VCA says at least weekly. The CDC says to clean turtle supplies outside if possible, or in a laundry sink or bathtub that you disinfect afterward. Keep turtle water away from kitchen sinks.

Should a turtle tank have sand or gravel?

Most turtles do best on a bare bottom. VCA warns that turtles often swallow sand and gravel, which can block the gut, and the Animal Medical Center says no substrate is best. Smooth stones too big to swallow are the safer choice. Softshell turtles are the exception, since they need sand to bury themselves.

Does a turtle tank need a heater?

Usually, yes. VCA says a water heater should keep the water at 75 to 82 F. If your room stays in that range all year, the heater can stay off. Basking spots run warmer: VCA gives 75 to 88 F and MedVet gives 85 to 90 F. Check both temperatures with a separate thermometer.