Mexican Red Knee Tarantula Care Sheet

Mexican Red Knee Tarantula Care Sheet

The Mexican red knee tarantula (Brachypelma smithi) is a 5.5-6.5” diameter, nocturnal, terrestrial tarantulas native to eastern Mexico. They prefer to live in arid environments such as desert and scrub, although they also sometimes live in forested areas.

Mexican red knee tarantulas are fairly traditional tarantulas in shape. They have black bodies bodies with characteristic orange “knees” on their legs, which gave them their name. Like many tarantulas, they have urticating hairs. They are also technically venomous, although it is not dangerous to humans.

Mexican red knee tarantulas make good pets because of their docile nature and general hardiness. When cared for properly, males generally live up to 10 years, and females may live well beyond 15 years.

Minimum terrarium size for Mexican red knee tarantulas

The minimum terrarium size for a Mexican red knee tarantula varies depending on its size. Slings can be housed in basic acrylic spiderling enclosures, no smaller than four legspans by three legspans. These should be gradually upgraded until they are large enough to be comfortable in an adult-sized enclosure no smaller than 20”L x 10”W x 10”H, or a 10 gallon tank, although taller (and larger in general) is likely to be better.

Housing multiple tarantulas in the same terrarium is not recommended, and is likely to result in cannibalism if attempted.

Do Mexican red knee tarantulas need UVB?

Mexican red knee tarantulas are generally kept without UVB lighting, as they have proven to be capable of surviving without it, and considering that UVB wavelengths are blocked by glass and acrylic, installing the lamp can be tricky. 

However, there is some evidence to suggest that tarantulas may benefit from UVB lighting when appropriately provided. This paper speculates that wild tarantulas may get at least part of their vitamin D3 from UVB exposure, and this paper provides evidence of invertebrates being able to synthesize vitamin D3 from UVB.

If you want to provide UVB for your tarantula, the best bulb to use will be a compact coil Zoo Med Reptisun 5.0 13w, mounted horizontally in a reflective fixture. Place this lamp on top of a mesh lid with holes large enough to prevent the spider from getting its feet caught, so you may want to wait to provide UVB lighting until the tarantula has grown large enough for an adult enclosure. UVB output decays with age, so the bulb must be replaced every 6 months to maintain performance.

Lights should be on for 12 hours/day.

Best temperature for Mexican red knee tarantulas

Mexican red knee tarantulas should be kept between 70-80°F. If your room temperature in on the cooler end of that range, it’s a good idea to stick a heat mat to one side of the enclosure and connect it to a thermostat set to 80-82°F. This creates a temperature gradient so your tarantula can pick how warm or cool it wants to be. 

Use a digital probe thermometer to keep track of enclosure temperatures.

Best humidity levels for Mexican red knee tarantulas

Mexican red knee tarantulas prefer moderate humidity levels between 40-60%, with occasional spikes up to 80%. For slings and juveniles, this can be done by slightly moistening the substrate. For adults, it’s best to simply provide both dry and moist areas in the enclosure. When moistening the substrate, make it slightly damp, not saturated. 

Measure the ambient humidity levels with a digital probe hygrometer.

Best substrate for Mexican red knee tarantulas

Although Mexican red knee tarantulas are not commonly known to burrow in captivity, they are known to burrow in the wild, so it’s still a good idea to offer them that choice. Slings should have around 2-3” of substrate, depending on size, and adults should have at least 4”. 

We recommend the following substrates for Mexican red knee tarantulas:

  • Zoo Med Eco Earth
  • Zoo Med ReptiSoil
  • Exo Terra Plantation Soil

How to decorate a Mexican red knee tarantula terrarium

An empty terrarium can lead to a stressed tarantula, and it’s not much to look at, either. At bare minimum, you will need at least one hiding spot for the tarantula to use. However, you can also include other decorative items, such as:

  • small logs and branches
  • cork flats/tubes
  • live or artificial plants
  • artificial ornaments

What to feed to a Mexican red knee tarantula

Mexican red knee tarantulas are primarily insectivores, although they are known to eat small vertebrate prey in the wild. As pets, they should get a variety of insects to get the right nutrition. Slings should be fed every 4-7 days, juveniles should be fed every 7-10 days, and adults should receive a meal every 14 days or so.

Offer 1-5 appropriately-sized insects per feeding, depending on the tarantula’s body condition and the size of the insect. Each insect should be small enough for the tarantula to easily overpower, especially for slings, which is roughly the same length as its abdomen.

Feeder insect options for Mexican red knee tarantulas: crickets, dubia roaches, discoid roaches, red runner roaches, black soldier fly larvae, mealworms

Flightless fruit flies are a good option for particularly small slings.

Uneaten prey should be removed 24 hours after offering.


Of course, don’t forget a small water bowl for your tarantula to drink from! If it’s too small for a water bowl (under 2” diameter), then mist the enclosure occasionally to create water droplets for it to drink. Change the water dish daily and scrub it out with a reptile-safe disinfectant weekly.

Adding a sponge to the water dish is usually unnecessary.

How to handle your Mexican red knee tarantula

Tarantulas don’t appreciate petting and handling in the same way that dogs and cats do. That being said, Mexican red knee tarantulas have a docile, if skittish, temperament, and can tolerate human interaction fairly well. More skittish individuals are likely to shoot hairs when startled.

If you wish to pick up your pet, simply allow them to crawl onto your hand, and keep your movements slow. Handle them over a soft surface, like a bed or couch, to cushion them in case they fall. Handling should not be done frequently, however.

*This care sheet contains only very basic information. Although it’s a good introduction, please further your research with high-quality sources. The more you know, the better you will be able to care for your pet!

"Mexican Red Knee Tarantula" by wwarby is licensed under CC BY 2.0

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Hengqian Yao

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