Albino axolotl eating an earthworm. Photo credit: mrturtle995
Introduction
In this article, we will discuss the primary types of food that are fed to axolotls. Earthworms have been seen as the ideal diet for axolotls for many years, and they remain to be the best option when nutritional content is considered.
Earthworms
There are roughly six varieties of worms used to feed axolotls. The earthworms we refer to here include varieties colloquially known as nightcrawlers, red wigglers, or gray worms. Scientifically referred to as the Lumbricidae family, these are considered the safest and most nutritionally complete food available to feed axolotls longer than 7.5 cm (3 inches).
Table 1. Data on the nutritional content of numerous species of earthworms.
| Protein (dry) | Fat (dry) | Calcium (dry) | Calories per Gram | Moisture | Ash | Fiber |
Lumbricus terrestris | 56.1% - 60.7% | 4.4% | 1.52% | 4 | 81.1 | 11.4-28.7 | N/A |
Aporrectodea caliginosa / Allolobophora chlorotica | 62.2% | 1.77% | 1.72% | N/A | 78.3 | 35.2 | N/A |
Eisenia fetida (Red Wiggler) | 54.6%-70.42% | 1.89% | 1.72% | 2.99 | 83.3 | 10.8 | 0.7 |
Perionyx excavatus | 46.57%-60.25% | 8.03%-9.18% | N/A | N/A | N/A | 5.14 | N/A |
Eudrilus Eugeniae | 56.4% | 7.9% | N/A | N/A | 85.3 | 13.1 | 5.9 |
All earthworms are nutritionally appropriate for axolotls. They meet their dietary needs with >45% protein, a high calcium content, and they are high in calories.
Common Names for Worm Species and Their Identification
Below is a detailed description of different worm varieties, as well as identification methods. The methods of identifying earthworms primarily consist of counting segments and observing color.
Lumbricus terrestris:
Common names: Nightcrawler, Canadian Crawlers, tiger worms, bait worms, fishing worms
Identification: 10-25 cm in length, reddish cream in color, 32-35 segments before their cl*tellum.
Canadian nightcrawler worm. Photo credit: Thibaud Decaens
Aporrectodea caliginosa / Allolobophora chlorotica:
Common names: Gray worm, British worm, field worm
Identification: 4-10 cm in length, pale grayish-pink in color, ~25 segments before their cl*tellum.
Gray worms. Photo credit: Ross Gray
Eisenia hortensis:
Common names: European Nightcrawler, Dendrobaena veneta, Dendrobaena hortensis, Dendra
Identification: 12-20 cm in length, brown-red in color, 25 segments before their cl*tellum.
European nightcrawler. Photo credit: Devin Gustus
Eisenia fetida:
Common names: Red Wiggler, compost worm, banded worm, manure worm, trout worm, brandling worms.
Identification: 5-7 cm in length, deep rust-red in color, ~25 segments before their cl*tellum.
Red wiggler earthworm. Photo credit: BiasLabs Ltd
Eudrilus eugeniae:
Common names: African Nightcrawler
Identification: 20-30 cm in length, grayish-purple color, ~13 segments before cl*tellum.
African nightcrawler worm. Photo credit: Devin Gustas
Perionyx excavatus:
Common names: Compost worm, red wiggler 'variety pack', blues, Indian Blues
Identification: 6-8 cm in length, bluish red color, 12 segments before cl*tellum.
Perionyx excavatus worm. Photo credit: Scientific Report
Additional Axolotl Foods
Axolotl diets can be successfully varied, so long as nutritional benefits and potential detriments are considered. Below is a list of potential foods that may be occasionally supplemented, including foods for hatchlings and under-researched crustaceans that may be fed.
Table 2. Data on the nutritional content of additional food options.
| Protein % | Fat % | Calcium % | Ca:P |
Tubifex | 46.1 | 15.1 | 0.19 | 0:26 |
Blackworm | 47.8 | 20.1 | 0.11 | 0:12 |
White Worm | 70 | 14.5 | N/A | N/A |
Grindal Worm | 70 | 14.5 | N/A | N/A |
Daphnia | 55.2 | 6.6 | 0.1 | 0.08 |
Brine Shrimp | 55 | 14 | 5 | N/A |
Springtails | 55.4 | 28 | 26.9 | N/A |
Scuds | 40 | 5.5 | 4.1 | N/A |
Bloodworms | 52.8 | 9.7 | 0.38 | 0:42 |
Isopods | 41.2 | 11.5 | 14.38 | 12:1 |
Blackworms and tubifex worms are the primary high-protein diet preferred for hatchling axolotls, however, using earthworms and brine shrimp in excess tends to result in healthier axolotls. The reason for this is currently unknown, however it may be tied to the calcium to phosphorus ratio required by axolotls, which is 2:1. Crustaceans are a popular choice for introducing high levels of calcium into the diet, however care must be taken to prevent internal impaction caused by high fiber and chitin diets.
Tubifex/Blackworms
Tubifex tubifex/Lumbriculus variegatus
Live blackworms. Photo credit: Ethical Axolotls
This is a food best used for hatchling axolotls that are big enough to have started growing in their legs, but still too young to eat cut up earthworms.
Best cultured in cool or room temperature water in a gravel substrate, harvested with turkey baster. Can reproduce by splicing.
Perform water changes frequently.
For storage, keep in a tub of fresh water in the refrigerator, rinse with dechlorinated water daily.
Tubifex and blackworms have similar care and culturing requirements, however live Tubifex are unavailable in the US as of 2023.
White Worms/Grindal Worms
Enchytraeus sp./Enchytraeus buchholzi
Photo credit: Ethical Axolotls
White worms are best fed to young axolotls, from hatchlings to 4 months of age.
Best cultured in a temperature between 55°-70°F. Culture on coco coir, worm castings, or organic top soil.
Feed moist or soaked grains. Place food over a grate such as embroidery backing for easy harvest.
Allow the food to mold slightly before removal.
Harvest with tongs, rinse in clean water before feeding. Change substrate when it becomes too moist and the worms begin to climb the walls of the enclosure.
Daphnia/Scuds
Daphnia pulex, daphnia magna/gammarus, amphipoda
Daphnia. Photo credit: Ethical Axolotls
Daphnia. Photo credit: Ethical Axolotls
Baby daphnia or brine shrimp are best used for feeding newly hatched axolotls. Regular daphnia can be fed to hatchling axolotls that are a bit larger than new hatchlings and able to eat the larger adult daphnia.
Best cultured in cool or room temperature water. Provide a photoperiod of at least 16 hours per day.
Provide a cycled tank with a seeded sponge filter.
Feed yeast or spirulina powder, in minimal amounts. Perform small water changes whenever Nitrates rise to 10 ppm.
Brine Shrimp
Artemia
A hatchling axolotl in a tub filled with baby brine shrimp to feed on. Photo credit: Ethical Axolotls
Baby brine shrimp are best used for feeding newly hatchedaxolotls
Raise in room temperature or heated water, with a salinity of 35-40 ppt (specific gravity 1.024-1.028). This measures to around 1 ½ tablespoons of aquarium salt per liter of dechlorinated water. Provide constant light and high flow to force the brine shrimp eggs to remain suspended.
Consider using airline tubing for aeration, and either a premade hatchery or one homemade with a plastic 2L bottle. A cycled filter is not required for hatching BBS to feed.
Collect with a baby brine shrimp net, rinse before feeding. Adult brine shrimp may be fed spirulina powder.
Springtails and Isopods
Collembola/Isopoda
Springtails. Photo credit: Ben Gruver
Isopods. Photo Credit: Ethical Axolotls
Isopods are best fed to adult axolotls 15 cm (6 inches) and larger, while springtails are best fed to axolotls that are at least 5 cm (2 inches) long.
Culture on coco coir, clay, or soil. Feed detritus that is rich in nutrients, such as old grain and small amounts of rotten fruit.
Provide calcium supplements such as cuttlebone, snail shells, or fish bones.
Harvest isopods with tongs, or catch with hands. Harvest springtails by lifting a piece of hardscape with springtails on it, holding it over the collection container, and tapping against the side of the hardscape until they fall off.
Note: Springtails float.
Bloodworms
Chironomidae
Thawed out frozen bloodworms. Photo credit: Hika's Treasures
Bloodworms can be fed to any axolotl older than a hatchling.
Bloodworms are best sourced frozen, due to their life cycle ending in the adult midge fly.
Thaw bloodworms in a cup of water before feeding. Feed sparingly due to low nutritional value.
Nutritionally Insufficient Foods
Although many different foods have been tested through trial and error to provide variety in axolotl diets, there is mixed success to be found in feeding foods other than earthworms. Many types of meat are very fatty compared to worms, and feeding dried food too often may risk constipation or impaction. The below foods are considered inadequate for a sustained diet, and should either be fed sparingly or not at all.
Table 3. Nutritional content of foods considered insufficient for staple axolotl foods.
| Protein % | Fat % | Calcium % | Risks |
Hikari Sinking Carnivore Pellets | 47 | 5 | N/A | Constipation, bloating, obesity, impaction |
Rangen Salmon Pellets | 45 | 18 | N/A | Constipation, bloating, obesity, impaction |
Feeder fish | 15.75 | 3.34 | N/A | Thinaminese toxicity (depending on species) resulting in vitamin B deficiency, causing seizures and scoliosis |
Repashy Grub Pie | 43 | 10 | 1.4 | Minimal risk |
Neocaridina | N/A | N/A | N/A | Minimal nutritional information available, feed as treat only |
Beef products | 76.9 | 20 | 0.03 | Excessive uric acid production, visceral gout, renal failure, calcium deficiency |
Salmon | 63.5 | 34.2 | 0.039 | Diarrhea, excessive uric acid production, visceral gout, renal failure, calcium deficiency |
Many of the above foods have an inappropriate calcium to phosphorus ratio. Others are high in fat content and therefore are dangerous to feed, and many pellets are nutritionally incomplete as well. Repashy Grub Pie may contain the necessary nutrients to sustain an axolotl, though being composed of ground black soldier fly larvae, it may be too fibrous for continual usage.
Overall, earthworms are still considered to be the primary food source that is appropriate for all axolotls. The type of earthworm is not important, so long as they can be verified as parasite and disease-free. Additional snacks may be fed, however, earthworms should always be the primary food source, to meet both protein and calcium nutritional requirements.
Sources and Additional Reading
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African Night Crawler. Worm Farm Facts - African Night Crawler. (2012). http://www.wormfarmfacts.com/African-Night-Crawler.html#:~:text=African%20Night%20Crawler%20are%20a,is%20compared%20to%20the%20redworm
Bou-Maroun, E., Loupiac, C., Loison, A., Rollin, B., Cayot, P., Cayot, N., ... & Medina, A. L. (2013). Impact of preparation process on the protein structure and on the volatile compounds in Eisenia foetida protein powders. Food and Nutrition Sciences, 4(11), 1175.
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