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Diamondback terrapins (Malaclemys terrapin) Care – Jonathan Helms

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Related pages on the WCT site:

Diamantrug schildpadden (Malaclemys terrapin)  – Jonathan Helms

菱斑龜/鑽紋龜(Malaclemys terrapin) 的飼養指南 作者 (Big 5) Jonathan Helms

菱斑龟/钻纹龟(Malaclemys terrapin) 的饲养指南    作者 (GB):  Jonathan Helms

Malaclemys Gallery

Basking Turtles -- Chrysemys-Trachemys-Pseudemys-Deirochelys-Graptemys-Malaclemys - Jody Karlin

Understanding Biological Filtration - Jody Karlin

Water Chemistry: pH, GH and KH What are they all? -   Scott Thomson


Related pages on the web: 

Diamondback Terrapin World

Diamondback Terrapins


This care sheet is intended only to cover the general care of this species. Ongoing research to best develop a maintenance plan for whichever species you are caring for is essential.


Diamondback terrapins (Malaclemys terrapin) are arguably one of the most beautiful of all turtle species when compared to other species native to the United States and worldwide. While other species have their adherents, no one could ever say that Diamondback’s, with their beautifully patterned markings, are drab.  Until recently, poorly understood environmental conditions have given this species a reputation as a poor husbandry choice and even as a difficult animal to maintain in captivity.  The efforts of numerous people have combined to now make this a viable and sought after species for the intermediate and advanced keeper. Try to obtain captive-bred Malaclemys for pets. These will generally be healthier and much better adapted to captivity than wild caught specimens.


Malaclemys terrapin live in brackish water ranging from marsh areas near the ocean to islands surrounded by pure salt water.  Diamondback terrapins range from Cape Cod, Massachusetts to Corpus Christi, Texas.  In the wild they mostly feed on clams, shrimp, crabs, snails, and small fish.  They have been known to eat some vegetation but they are primarily carnivores.

To Salt or Not to Salt

This is the question most often asked about this species. The answer is unfortunately:  yes and no.  There are many examples of people successfully keeping this species in fresh water and just as many examples of people failing to be able to do so yet having failing animals turned around by exposure to brackish water. . The following advice is offered as the best combination of conditions offering the greater chances of success.


Wild caught adults need be kept in brackish water, fresh wild caught specimens must be kept in brackish water with a specific gravity of 1.018 measured with a hydrometer* (see note below)  for the first six months. This can then be lowered down to 1.014 to 1.016.  Without salt most wild caught animals will develop shell rot and have buoyancy problems.  At salinity levels of 1.014 or above diamondback terrapins will need to be placed in fresh water at least once a week.  Their body can take in brackish water and filter out the salt up to a certain level then they will stop drinking.  When placed in fresh water they can drink enough water in five minutes to last them over a week.  In the wild they can be seen drinking from small puddles, leaves, and even other terrapin’s shells during the rain.  Rock salt is an inexpensive and commonly used salt to raise the salinity level. 


Captive born hatchlings and adults normally can be kept in fresh water.  If they start to develop shell rot they will need to be moved to brackish water (1.014 to 1.018).




Hatchling and juvenile diamondback terrapins should be fed a mixture of commercial foods and for a treat they can be fed small live food.  They are not the best hunters and can rarely catch live feeder fish.  Only feed them once a day, and as much as they can eat in fifteen minutes.


Adults should be fed every other day.  Adult females can get very over weight if they are fed too much.  In some cases over feeding has resulted in death.


Many wild caught adults will not eat commercial food and will need to be fed seafood.  Smelt is a very common type of fish used for feeding.  If you have a problem getting them to eat smelt or other small fish try shrimp.  Make sure to freeze all seafood not immediately used and completely thaw it before feeding it to your diamondback terrapins.  Freezing the fish destroys the vitamin E, which is important for diamondback terrapins health.  If your diamondback terrapins are not eating commercial foods you can take vitamin E pills and crush them up and put them inside the thawed fish.


Diamondback terrapins are very messy eaters, their jaws are used to crush shellfish in the wild and they will crush every thing they eat.  Feeding them separate from their tank will help keep their water much cleaner.


Hatchlings can be kept in a 10 gallon aquarium filled nearly to the top, they need basking platforms, and basking lights.  In one corner of the environment a hardware store reflector clip light lamp should be positioned to provide artificial basking facilities. This should be positioned to provide a basking spot of 90 degrees F or so (32 degrees C) on the basking platform.   The habitat should also be equipped with a full spectrum fluorescent light to provide for UVB. A UVB source is necessary for Vitamin D3 syntheses (needed in calcium metabolism). If preferred to this lighting arrangement a Mercury vapor bulb may be used that fulfills all requirements. Live or plastic aquatic plants are suggested to provide a sense of security and hiding places.


Filtration is very important to hatchlings and if the water isn’t kept very clean they will develop skin problems.  Submergible filters don’t work very well for diamondback terrapins. Hang-on or canister filters work much better.  The water temperature should be kept around 25 degrees C (78 F).  Diamondback terrapin hatchlings normally grow very quickly and will reach 10 cm (4 inches) within the first year.  They will grow out of a 10 gallon aquarium very quickly. 


After the first year their growth rate drastically slows down.  Females mature in about 4 to 5 years and can reach up to 22 cm (9 inches).  Males mature faster in about 3 years but they only get up to 15 cm (6 inches), which makes them ideal for pets.  Adult males should be housed in a minimum of 75 gallons but females need a minimum of 100 gallons.  100 gallon stock tanks, for horses, work very well for housing.  They offer water depths of two feet and lots of surface area to swim around. 


Crushed coral works great for a substrate.  In the wild females can be found grazing on coral, this gives them extra calcium and helps keep their beak from getting over grown. Avoid having large rock in their tanks as they can nick and chip their shells leaving them susceptible to shell rot or other fungus infections.


Predator proof outdoor habitats offer many advantages over indoor accommodations and should seriously be considered as an option during warm weather. A child’s wading pool sunk into the ground in a secure enclosure makes for a serviceable outdoor habitat.  Larger ponds with advanced filtration can be used to provide a spectacular outdoor home for your Diamondback.     




Diamondback terrapin are not aggressive turtles but if they are over crowded, especially juveniles, they have been known to nip at each others feet.  Separating the ones with such wounds and allowing their feet to heal along with moving them to a larger tank should stop the biting.


Basking is very important for adults.  Females shed their scutes once a year and if they don’t bask water will get trapped under the loose scutes and cause shell rot.  Males only shed once every three to four years.


Additional information:


It should be noted that turtle and tortoise care research is ongoing. As new information becomes available we share this on our web sites. Please check back often to see this updated information at  Jonathan Helm’s Diamondback Terrapin World at  and  the World Chelonian Trust web site at . Serious keepers find it to be a benefit to have the support of others who keep these species. Care is discussed in our free online email communities, which may be joined from the web addresses above.


* Specific gravity is a ratio of the mass of a material to the mass of an equal volume of water at 4 degrees C (39 F). Because specific gravity is a ratio, it is a unitless quantity. For example, the specific gravity of water at 4 degrees C is 1.0 while its density is 1.0 g/cm3.  This is measured easily with a hydrometer purchased at any pet shop or online store that caters to the salt-water fish hobby.  Good floating glass hydrometers are usually 25 to 30 cm (10 to 12 inches) tall. Some are equipped with a thermometer. - World Chelonian Trust


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