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Black Knobbed Map Turtle Care Guide

When it comes to the care of black-knobbed map turtles, simplicity and moderate tank requirements are key. Belonging to the Graptemys genus, this small to medium-sized Alabaman turtle, also known as the black-knobbed sawback turtle, features distinctive spikes on its back.

This guide will provide you with essential information to ensure the well-being of your black-knobbed map turtle, with an emphasis on tank maintenance made easy.

Black Knobbed Map TurtleFacts and Information

Black knobbed map turtle close up from behind showing black markings on top of shell points
Black knobbed map turtle close up from behind showing black markings on top of shell points
  • Experience Level: Beginner
  • Family: Emydidae
  • Scientific Name: Graptemys nigrinoda
  • Average Adult Female Size: 4 to 8 inches
  • Average Adult Male Size: 3  to 4 inches
  • Lifespan: 20 to 30 years
  • Clutch Size: 10 eggs
  • Egg Incubation Period: 60 to 82 days
  • Food: Commercial turtle diet
  • Tank Size: 25 to 75 gallons
  • Average Temperature: 85°H/70°L
  • UVB Lighting: Needed
  • Average Price Range: $100 to $200
  • Conservation Status: Nar Threatened on IUCN Red List

The black-knobbed map turtle is a North American turtle that can be found in the southeast. They belong to the genus Graptemys and the family Emydidae.

The black-knobbed map turtle can be distinguished from other map turtles by the black knobs at the end of the spokes on their keels. There are two subspecies of the species Graptemys nigrinoda.

These include the northern black knobbed map turtle (G. n. nigrinoda) and the southern black knobbed map turtle (G. n. delticola). While the southern black knobbed map turtles have markings on their plastrons, northern black knobbed map turtles lack such markers.

Male generally attain carapace lengths of 3 to 4 inches, while females attain carapace lengths of 4 to 8 inches.

These turtles are endemic to the Mobile Bay drainage in Alabama, the  Tombigbee River system, and in the Black Warrior River in Mississippi. Unlike other North American turtles, the species Graptemys nigrinoda can only survive in freshwater.

If you are unsure about what type of map turtle you have we have care sheets on the Ouachita Map Turtle, Northern Map Turtle, Texas Map Turtle, False Map Turtle, Barbour’s Map Turtle, and the Mississippi Map Turtle.

Black Knobbed Map Turtle Care Sheet

Black Knobbed Map Turtle Habitat

As already mentioned, the black-knobbed map turtle is strictly a freshwater turtle. It inhabits sand and clay-bottomed streams in the Tombigbee and Black Warrior river systems.


Tetra Glass Aquarium 55 Gallons, Rectangular Fish Tank (NV52018)

As small turtles, black knobbed map turtle does not require too much space. An adult male needs about a 25 to 30-gallon tank; while the larger adult females need a 75-gallon aquarium.

A larger aquarium is always preferable as map turtles are lively swimmers. Also, two or more map turtles can be housed in an aquarium.

Similarly, you can house them with cooters, sliders, and other North American turtles. To ensure all the turtles are comfortable, add 20 gallons of tank space for each additional turtle.

It is best to start juveniles in a small aquarium (such as a 10 to 20-gallon aquarium). Alternatively, you can fill an adult-sized aquarium with less water.

Since chlorine and chloramine are harmful to the black-knobbed map turtle’s eyes, you need to only use dechlorinated water for the turtle’s tank.

If you are using tap water for the aquarium, then it needs to be treated with an aquarium water conditioner such as the Natural Rapport Aquarium Water Conditioner. This water conditioner detoxifies heavy metals, as well as neutralizes both chloramine and chlorine in tap water.

All aquariums need a filtration system. This ensures waste is filtered out of the water. Dirty water can lead to infections. A good filter to use is the SunSun HW-302.

This powerful aquarium filter will successfully keep the water clean. In addition to this, you have to change the water in the aquarium monthly. Use an aquarium vacuum cleaner to suck out all the water and replace it with new water.


I recommend that you go with a bare-bottom aquarium if you are a beginner. As there is no substrate, cleaning is easy. Additionally, there is no substrate for the turtle to accidentally ingest.

Since substrates can add to the aesthetics of the tank, you may want to add some. If you must, go with large substrates such as river pebbles as they are hard to ingest. The Aquarium Gravel River Rock on Amazon is an excellent choice.


The temperature needs of this turtle are easy to meet. The water temperature needs to be in the low to mid-70s. The basking temperature needs to be in the high 80s to the low 90s. And finally, the air (ambient) temperature needs to be in the low to mid 80’s.

If you have a problem maintaining the water temperature given, use a submersible heater. You may not need a heater since the temperatures are in the ballpark of what is to be expected at room temperature.

If you are using a submersible heater ensure it’s protected with a guard and that the water doesn’t overheat. Use a thermostat such as the Inkbird Heating Thermostat to control the temperature.

There are several basking lamps to choose from. I recommend ceramic heating lamps. They may be more expensive but they last longer and do not emit light. This means it can be on even at night.  Use a thermostat such as the BN-Link thermostat to monitor the temperature.

Thermometers to use include Zacro LCD Digital Aquarium Thermometer for the water and Zoo Med Repti Temp Digital Infrared Thermometer for the basking spot.


The black knobbed map turtle needs UVB light to produce vitamin D3. As such, a fluorescent light such as the ReptiSun is a must. Of course, sunlight is the best source of UVB but since sunlight can quickly heat the aquarium to dangerously high levels, UVB light is the next best thing for a turtle kept indoors.

Make sure the lights are on for 12 hours a day and off for the next 12 hours. To ensure the lights are turned off and on at the right time everyday invest in a timer. A programmable digital timer is best.


Map turtles are avid baskers and the black knobbed map turtle is no exception. Make sure to provide a large enough basking platform. This ensures that no part of the turtle touches the water as it basks.

If you have several North American turtles housed in the same aquarium, expect them to bask at the same time. As such the basking platform or ramp needs to be large enough to accommodate all the turtles at the same time.

You may need to custom-build a platform large enough for all the turtles. If you have a few turtles, the OASIS #64226 Turtle Ramp is a good choice. It is sturdy, large, and easy to install.

Feeding the Black Knobbed Map Turtle

While most turtles are omnivorous, aquatic turtles are generally more carnivorous and the black knobbed map turtle is no exception. Feed this turtle a high-protein diet.

However, make sure not to overfeed the turtle as this can lead to pyramiding of the shell and other health problems that can shorten the turtle’s life.

I recommend making a good commercial turtle diet the main staple of the turtle’s diet since they contain all the needed nutrients in the right amount.

Also, they are fortified with dietary vitamins and nutrients which means you don’t need to supplement the turtle’s diet separately. Some of the best commercial turtle foods include Fluker‘s Aquatic Turtle Diet, Mazuri Aquatic Turtle Diet, and Tetra Reptomin Floating Food Sticks.

Supplement the commercial diet (which I recommend should make up about 80% of the diet) with animal protein such as shrimp, earthworms, crayfish, feeder fish, mealworms (Breed your own mealworms), bloodworms, crickets(start a cricket farm), and other insects.

Leafy greens are high in fiber and calcium. These can be fed to the turtle every day and as much as the turtle needs. I recommend romaine lettuce and anacharis.

Other suitable plants include pondweed, water hyacinth, water lilies, frogbit, duckweed, hornwort, and other edible sea greens. Also feed them squash, endive, escarole, kale, mustard green, zucchini, and other leafy greens that are easier to find.

Do not feed the turtle meat or mice. Also avoid feeding the turtle fruits, and iceberg lettuce.

Feed adults once every other day. This includes all turtles that are more than 6 months old. Hatchlings and juveniles should be fed every day. Feed them until they show a diminished appetite.

Black Knobbed Map Turtle’s Temperament & Handling

The black knobbed map turtle is a display pet and shouldn’t be handled unless it’s necessary. Specimens are generally skittish and will shy away from human contact. As they come to associate you, the keeper, with food, they may rush towards you when you approach the enclosure.

The black knobbed map turtle can be housed with other North American turtles. However, if there are signs of aggression, quarantine the aggressor.

Black Knobbed Map Turtle’s Lifespan

These species are long linked. With proper care, members of the species Graptemys nigrinoda can live for 20 to 30 years.

Common Health Concerns

Regardless of how well kept a pet turtle is, health issues can still arise. Some symptoms to be critical of include irregular growth such as shell pyramiding, cracked shell, cuts and bruises, gaping mouth and nose, swollen/sunken eyes, and a frothy nose.

Behaviors to be critical of include refusal to swim (or excessive basking), lethargy, and appetite loss.

Hypovitaminosis A- Inadequate amounts of vitamin A in the turtle’s diet can lead to swollen/sunken eyes, raw skin, loss of appetite, and lethargy. Correct vitamin A deficiency by providing supplements and relying on a good well-rounded commercial diet. Also, visit the vet.

Pyramided Shell– The main reason why turtle keepers are advised to not overfeed their turtle and to stick to a regular feeding schedule is to prevent overgrowth.

Overgrowth leads to the scutes on the carapace growing vertically more quickly than they do horizontally. When noticed early (in the first 2 years of the turtle’s life), shell pyramiding can be corrected.

Infection – Skin, shell, and ear infections can be both unsightly and harmful to the turtle. This is usually down to poor husbandry, in particular, unhygienic tank water. To prevent this, change the water in the aquarium regularly and provide a powerful filter.

Cuts and bruises – Pinpointing the cause of a cut or a bruise can be difficult but must be done when your pet black knobbed map turtle appears to have them. If it’s a sharp edge in the aquarium, remove the object with a sharp edge. If it’s a fellow rank mate causing the bruising and cuts, relocate the aggressive turtle.

Pricing and Availability

The black knobbed map turtle is one of the more popular map turtles kept as pets. This may be because they are small turtles and require less space than other map turtles do. Regardless of the reason, the black knobbed map turtle is easy to find. The best bet of a healthy baby black knobbed map turtle is through a breeder.

Some online sites where you can get in touch with reputable breeders include Turtle Source, Fresh Marine, and Underground Reptiles. The black knobbed map turtle generally costs between $100 and $200.


On the IUCN Red List, the Graptemys nigrinoda has a lower risk status of near threatened. As such, although they may not be threatened at the moment, they will be in the future if they are protected.

The main threats to the wild populations of the species include habitat degradation and human activities. Humans are known to remove logs on shorelines. Logs that the species bask on. Also, fishing equipment such as hoop nets, and trotlines may accidentally keep members of the species.


The small black knobbed map turtle is a wonderful pet to keep. They are lively, hardy, and full of energy. Feeding them is easy and they require small aquariums.

However, when acquiring a turtle, it is important to keep in mind that, they are display pets. Unlike other reptiles such as snakes and even bearded dragons, the map turtle gets extremely stressed when held.

Ensure aquarium conditions are kept right and they are well-fed but not overfed. If you have any suggestions or questions, leave a comment.

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Judith Bautista Garcia

Friday 28th of August 2020

How often I have to feed my turtle, once a day or two? and how much ? thank you.