What do red-eared sliders eat?

Diet by life stage

Red-eared sliders (Trachemys scripta elegans) are omnivores whose diet inverts dramatically with age. Hatchlings need protein for fast growth; adults need fibre and calcium-rich plant matter to avoid obesity and shell pyramiding. Per PetMD's slider care sheet and The Bio Dude's care sheet:

Protein sources

For hatchlings and juveniles, protein needs to provide steady growth without excess fat. Modern recommendations from TurtleHolic's care guide:

• Commercial pellets (staple) — Mazuri Aquatic Turtle Diet, Zoo Med Natural Aquatic Turtle Food (Growth Formula for juveniles, Maintenance Formula for adults), Tetra Reptomin. Fortified with calcium and vitamins. The base of the protein side of the diet.
• F/T bloodworms (variety) — small frozen-thawed blood worms available at aquarium stores.
• Earthworms (variety) — F/T or freshly killed, sliced into age-appropriate sizes for juveniles.
• Insects (variety) — F/T crickets, dubia roaches, BSFL — occasional supplements.
• Small fish (occasional treat) — minnows, guppies. NOT goldfish — see below.
• Skip: cat/dog food (wrong protein/fat balance), processed meats, anything human-table.

Why avoid feeder goldfish: goldfish contain thiaminase, an enzyme that destroys vitamin B1 (thiamine). Repeated goldfish feeding causes vitamin B1 deficiency and neurological problems — documented across multiple species of fish-eating reptiles. Per Merck Veterinary Manual, this is one of the few diet-driven reptile health issues with clear causal evidence. Minnows and guppies are safer occasional choices.

Plant matter

Plants make up the increasing share of adult slider diet. Daily- safe staples (always available in the tank or feeding container):

• Romaine lettuce — safe daily; rotates well.
• Dandelion greens — high calcium, safe daily.
• Mustard greens — good calcium:phosphorus ratio.
• Collard greens — daily-safe staple.
• Escarole, turnip greens, endive — variety rotation.
• Aquatic plants (ideal) — duckweed, water lettuce, water hyacinth, anacharis, hornwort. Slider grazes naturally; they're also edible enrichment.

Daily rotation (not daily as the sole green):

• Bok choy, watercress, arugula.

Limit to 1–2 times per week:

• Kale — high oxalate (binds calcium).
• Spinach — high oxalate.

Never feed:

• Iceberg lettuce — nutritionally empty (~96 % water).
• Toxic plants — avocado, rhubarb leaves, onion family.
• Fatty greens that aren't actually greens.

Feeding mechanics

Two approaches:

In-tank feeding (simpler). Drop pellets in the water, allow the slider to eat in its own time. Remove uneaten food after 15–20 minutes to keep water quality high. Plants can stay in for grazing.

Separate feeding container (cleaner). Move the slider to a separate plastic tub of water during meals. Keeps the main tank cleaner. Adds handling stress and an extra step — used by some keepers but not necessary if filtration is adequate.

A floating feeding ring (sold at aquarium stores) keeps pellets contained for in-tank feeding — easier to spot-clean uneaten food.

Calcium and D3

Sliders need calcium for shell development and bone health. Two key sources:

• Cuttlefish bone (calcium block) — leave a piece floating in the tank as a free-choice gnawing surface. Slider gnaws as needed.
• Quality pellets are calcium-fortified. Combined with cuttlebone, this usually covers calcium intake.

Calcium absorption requires vitamin D3, which sliders synthesise in their skin under UVB exposure. Without proper UVB, no amount of calcium fixes the deficiency — calcium passes through. See the UVB guide.

Multivitamin powder dusted on pellets occasionally (every 2 weeks) covers trace nutrients. Most commercial pellets include multivitamin in the formula; over-supplementation is the bigger risk than under-supplementation if pellets are the primary food.

Feeding frequency

Adults often hand a piece of feeder behaviour when fed too often — they become greedy and may bite during pellet drops. Drop frequency to 2 times per week if your adult is showing both behavioural greediness and body condition issues.

Body condition

Check shell condition and weight monthly:

• Healthy shell: smooth scutes, no raised lumps, even coloration, hard surface that doesn't dent.
• Shell pyramiding: raised scutes like a stack of pyramid shapes — signals overfeeding (especially excess protein in juveniles fed adult-frequency pellets).
• Soft, pliable shell in a juvenile — calcium / D3 deficiency, often UVB-driven. See the shell rot guide for related shell signs.
• Visible fat deposits around the legs and base of the shell — obesity, reduce frequency.

What goes wrong

Common diet-related problems in captive sliders:

• Shell pyramiding — too much protein in juvenile phase continued into adulthood. Reduce pellet frequency; introduce more plants.
• Obesity and fatty liver — daily pellets in an adult, lack of swimming exercise (often paired with undersized tank — see the tank size guide).
• Metabolic bone disease — calcium / D3 deficiency, almost always inadequate UVB.
• Vitamin B1 deficiency — neurological issues from feeder goldfish; preventable by avoiding goldfish.

The broader husbandry context is in the pillar care guide; UVB setup in the UVB guide; water temperature in the water temperature guide.