Mexican Red Knee Tarantula Nutrition Guide: Optimal Diet and Feeding Schedule

Everything you need to know about feeding your Mexican Red Knee Tarantula, from dietary requirements and portion sizes to supplements and foods to avoid.

BLUF: Mexican Red Knee tarantulas (Brachypelma spp.) are obligate carnivores best fed live, gut‑loaded invertebrate prey sized no larger than the tarantula’s abdomen and offered on a schedule tied to life stage. Feed spiderlings every 2–3 days, juveniles every 5–7 days, and adults every 7–14 days; always provide a shallow water dish and gut‑loaded feeders to ensure adequate micronutrients — and consult your veterinarian if you see prolonged anorexia, abnormal weight loss, or molting problems.

Dietary requirements by life stage

Mexican Red Knee tarantulas are terrestrial, sit‑and‑wait predators that rely on invertebrate prey for complete nutrition. Their energetic and micronutrient needs change substantially with life stage:

• Spiderlings (newly hatched to ~6 months): High growth rates require frequent feedings. Offer appropriately sized prey every 2–3 days. Prey item should be pinhead crickets, newly hatched roaches, or fruit‑fly strains for the smallest spiderlings; size target = roughly 25–50% of abdomen width. Molting is frequent (every few weeks to months) and growth is rapid, so calories should be available but avoid overfeeding single oversized prey that can injure delicate legs or fangs.

• Juveniles/Subadults (~6 months to sexual maturity — typically 2–6 years depending on sex and husbandry): Growth slows but remains steady. Feed every 5–7 days for juveniles, stretching to every 7–10 days as they approach subadult size. Prey size can increase to ~50–100% of abdomen width. Prioritize high‑quality feeders that were gut‑loaded for 24–48 hours.

• Adults (mature males: ~3–6 years; females: up to 20–30+ years): Metabolic needs drop after maturity, especially in males after their final molt. Typical adult feeding rhythm is once every 7–14 days for healthy adults. For a 4–6 inch (10–15 cm) legspan adult female, one or two large dubia roaches or 1–3 medium crickets per feeding is typical. Females can fast for months during egg‑sacs or in poor conditions; males commonly reduce feeding before and after searching for mates.

• Protein and fat requirements are met by whole prey; tarantulas digest prey liquefied by digestive enzymes, so intact prey provides nutrients plus moisture.
• Micronutrients (especially calcium) are a concern because many feeder insects are relatively low in calcium relative to phosphorus. Gut‑loading feeders with calcium‑rich foods (calcium‑fortified rodent chow, leafy greens for roaches, commercial gut‑load mixes) 24–48 hours before feeding reduces nutritional gaps.
• Provide constant access to clean water. Use a shallow dish (see later section) — even desert/arboreal tarantulas need available water.

Feeding schedule and portion guidelines

A practical feeding plan balances frequency, prey size, and the tarantula’s physiological state (molting, gravid female, male reproductive behavior). The general rule is prey size roughly equal to or smaller than the abdomen width; frequency reduces with age.

Feeding frequency and portion guidelines (examples):

• Newly hatched spiderlings (first 0–3 months): feed daily to every 2 days. Use pinhead crickets or flightless fruit flies. Offer 2–5 tiny prey items or continuous access to a small container of appropriate prey; monitor to avoid desiccation or escapes.
• Spiderlings (3–6 months): every 2–3 days. 1–3 small crickets or newly‑hatched roaches per feeding.
• Juveniles (6 months–2 years): every 5–7 days. One medium cricket or 2–3 small crickets; or one appropriately sized dubia nymph.
• Subadults (2–4 years): every 7–10 days. One to three medium/large feeders depending on prey size.
• Adults (after maturity): every 7–14 days. One large roach or 1–3 medium crickets per feeding. Females in good condition may need occasional larger meals; males typically eat less after maturity.

• Use forceps to present prey to avoid accidental pinching of the tarantula during retrieval.
• Remove uneaten prey after 12–24 hours for spiderlings and after 24–48 hours for juveniles/adults to prevent feeder stress or damage to the tarantula.
• Watch body condition: a healthy adult Mexican Red Knee maintains a rounded abdomen but should not be excessively swollen. Rapid, significant changes merit veterinary evaluation.

Safe and unsafe foods, gut‑loading, and supplements

Safe, recommended feeder insects

• Dubia roaches (Blaptica dubia): Highly recommended — hardy, nutrient‑dense, low escape risk. Suitable for juveniles to adults. Offer medium to large sizes for adults.
• House/cricket species (Acheta domesticus): Widely available; feed every 5–14 days depending on size. Crickets are good protein sources but can be noisy and escape-prone.
• Banded crickets/locusts: Good for size variety; use sparingly to reduce chitin overload.
• Silkworms (Bombyx mori) and black soldier fly larvae (BSFL): Lower chitin, often highly digestible — excellent for growing spiderlings.
• Mealworms (Tenebrio) and superworms (Zophobas): High fat content — use sparingly as treats rather than staple diet.

• Wild‑caught insects: Risk of pesticides, parasites, or toxins — avoid.
• Fireflies/lightning bugs: Contain lucibufagins. Highly toxic and can kill predators quickly.
• Rodents (pinkies/fuzzies): Generally not recommended for Mexican Red Knee tarantulas. Very large prey can physically injure tarantulas, and vertebrate prey carries higher pathogen risk and may defend themselves. If used, only by experienced keepers for very large, mature females, and NEVER as a routine.
• Insects collected from treated lawns or near pesticides: never feed.

• Gut‑loading: Feed feeder insects a nutrient‑rich diet 24–48 hours before offering them. Use commercial gut‑load mixes or high‑quality rodent chow, fresh vegetables (leafy greens, sweet potato), and calcium powder in roach diets. This increases vitamin and mineral content available to the tarantula post‑consumption.
• Calcium/vitamin dusting: Arachnid veterinarians vary in recommendations. For Mexican Red Knee tarantulas, routine dusting is generally unnecessary if feeders are gut‑loaded. However, light dusting with a calcium supplement (no vitamin D3 for invertebrates typically) may be considered for fast‑growing spiderlings or when gut‑loading isn’t possible. Overuse of dusts can create residue and respiratory irritation — use sparingly.
• Water: A clean, shallow water dish (see next section) is essential — tarantulas obtain water both by drinking and from prey.

Practical feeding tips, molting, hydration, and health concerns

Feeding technique and safety

• Use long‑handled forceps to place prey at the front of the enclosure near the chelicerae. This limits accidental pinches to your hands and reduces stress on the tarantula.
• If feeding in a separate container (some keepers do this to prevent prey from hiding), ensure the temporary enclosure is secure and that substrate is minimal to avoid stress. Return the tarantula to its primary enclosure promptly.
• Remove uneaten prey: For spiderlings and small juveniles, remove uneaten prey after 12 hours; for larger juveniles/adults, remove after 24 hours to 48 hours.

• Tarantulas stop feeding before a molt (pre‑molt) and may refuse food for days to weeks. Signs include decreased activity, darkening abdomen, or refusal to take prey. Do not attempt to force‑feed.
• Never feed during or immediately after a molt. Wait until the exoskeleton (especially fangs) hardens — typically 3–10 days post‑molt for spiderlings, up to 2–3 weeks for larger adults depending on humidity and temperature.
• Offering prey too soon post‑molt can injure the tarantula because the fangs are soft and digestive systems are recalibrating.

• Water dish: For adults, a shallow dish 3–5 cm wide with a low lip is appropriate; for spiderlings use a small bottle cap or damp cotton spot to avoid drowning. Keep water clean; change every 2–3 days.
• Temperature and humidity: Mexican Red Knee tarantulas do well at 22–27°C (72–80°F) and relative humidity around 60–70% with a larger dry area in the enclosure. Too‑high humidity increases fungal growth and can impair molts; too low can cause desiccation. Adjust with substrate depth and occasional misting as needed.
• Molting frequency: Spiderlings can molt every few weeks; juveniles every 1–4 months; adults may molt once a year or less. Females can continue molting even when mature and live decades.

• Warning signs requiring professional attention: prolonged anorexia beyond normal pre‑molt behavior, progressive emaciation, abnormal posture or paralysis, repeated failed molts, wounds or infection, or sudden swelling of the abdomen.
• Routine veterinary care for arachnids is less standardized than for mammals, but an exotics/avian/invertebrate‑experienced veterinarian can assess nutritional deficiencies and systemic illness. If you are unsure about fasting, molt complications, or abnormal signs, consult your veterinarian.

Key Takeaways

• Feed Mexican Red Knee tarantulas live, gut‑loaded invertebrates sized no larger than the tarantula’s abdomen; spiderlings: every 1–3 days, juveniles: every 5–7 days, adults: every 7–14 days.
• Use safe, captive feeder insects (dubia roaches, crickets, silkworms); avoid wild‑caught insects and toxic species (e.g., fireflies). Gut‑load feeders 24–48 hours before offering.
• Always provide a clean, shallow water dish (3–5 cm for adults; bottle cap for spiderlings), remove uneaten prey promptly, and stop feeding before/after molts until the exoskeleton hardens.
• Monitor body condition and feeding behavior; if you notice prolonged anorexia, failed molts, or unusual physical changes, consult your veterinarian experienced with invertebrates.
• When in doubt, prioritize consistent feeding rhythms, quality gut‑loaded feeders, and environmental stability (22–27°C, ~60–70% humidity) to support healthy growth and molting in Mexican Red Knee tarantulas.

Frequently Asked Questions

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