Axolotl Nutrition: All About Worms

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 clitellum.

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 clitellum.

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 clitellum.

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 clitellum.

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 clitellum.

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 clitellum.

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 hatched axolotls

• 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

A Abo-Taleb, H., F Zeina, A., Ashour, M., M Mabrouk, M., E Sallam, A., & MM El-feky, M. (2020). Isolation and cultivation of the freshwater amphipod Gammarus pulex (Linnaeus, 1758), with an evaluation of its chemical and nutritional content. Egyptian Journal of Aquatic Biology and Fisheries, 24(2), 69-82.

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.

Building A Worm Bin. Worm Compost Puts Life Back in Your Soil and Health in Your Plants. (n.d.-a). https://www.sierra-worm-compost.com/building-a-worm-bin.html

Caudata Culture Articles - Nutritional values. (n.d.). Copyright 2000-2009 Caudata Culture. All Rights Reserved. https://www.caudata.org/cc/articles/foods2.shtml

Chakraborty, P., Islam, M. R., Hossain, M. A., Fatema, U. K., Shaha, D. C., Sarker, M. S. A., & Akter, T. (2021). Earthworm meal (Perionyx excavatus) as an alternative protein source to fish meal in feed for juvenile butter catfish (Ompok pabda). Aquaculture International, 29, 2119-2129.

Desertcart United States of America. (n.d.). Buy Axolotl Food 3/16" Soft Moist Sinking Pellets for Axolotls, Snails, Newts, Shrimp & All Fish. Rangen 3/16". . .1/2-lb Online at desertcart UNITED STATES. https://www.desertcart.us/products/168776335-axolotl-food-soft-moist-sinking-pellets-for-axolotls-shrimp-snails-tropical-fish-3-16-rangen-salmon-pellets

Do you have any analysis information on brine shrimp?. BrineShrimpDirect. (n.d.). https://www.brineshrimpdirect.com/about-us/frequently-asked-questions/do-you-have-any-analysis-information-brine-shrimp/

Earthworm Ecology. Earthworm ecology | Earthworm Society of Britain. (n.d.). https://www.earthwormsoc.org.uk/earthworm-ecology

Eisenia fetida. BiasLabs. (2019, December 17). https://www.biaslabs.co.uk/species/eisenia-fetida/

The Feeders ~ BUGS. BambooZoo. (n.d.). http://bamboozoo.weebly.com/the-feeders--bugs.html

Feeding Insectivorous Reptiles. Feeding insectivorous reptiles. (n.d.). https://www.lllreptile.com/articles/134-feeding-insectivorous-reptiles/

Gray, R. (2018, August 4). Grey Worm. Science Learning Hub. https://www.sciencelearn.org.nz/images/3628-grey-worm

Grindalworm starter culture for sale in India - www.microworms.in. Microworms. (2023). https://www.microworms.in/grindal-worms-starter-culture-for-sale-in-india

Gustus, D. (2023, June 19). How to identify the European Nightcrawler Composting Worm. Dengarden. https://dengarden.com/gardening/Identifying-the-European-Nightcrawler-Composting-Worm

Hasanuzzaman, A. M., Hossian, S. Z., & Das, M. (2010). Nutritional potentiality of earthworm (Perionyx excavatus) for substituting fishmeal used in local feed company in Bangladesh. Mesopotamian Journal of Marine Sciences, 25(2), 134-139.

Hertrampf, J. W., & Piedad-Pascual, F. (2003). Handbook on ingredients for aquaculture feeds. Springer Science & Business Media.

Memiş, D., Çelikkale, M. S., & Ercan, E. (2004). The effect of different diets on the white worm (Enchytraeus albidus Henle, 1837) reproduction. Turkish Journal of Fisheries and Aquatic Sciences, 4(1).

Michaels, C. J., Ferguson, A., McKendry, D., Newton-Youens, J., & Whatley, C. (2021). Failure to improve calcium content of earthworms (Dendrobaena veneta) through three methods of gut-loading. Journal of zoo and aquarium research, 9(2), 134-138.

PP, J. J. NUTRITIONAL ANALYSIS OF FISHES FED ON FORMULATED FEED.

Schmidt, J. M., Peterson, J. A., Lundgren, J. G., & Harwood, J. D. (2013). Dietary supplementation with pollen enhances survival and C ollembola boosts fitness of a web‐building spider. Entomologia Experimentalis et Applicata, 149(3), 282-291.

Serrano Jr, A. E., & Poku, G. (2014). Nutritive value of termite as fish meal supplement in the diet of freshwater prawns (Macrobrachium rosenbergii de Man) juveniles. Extreme Life, Biospeology and Astrobiology, 6(2), 63-71.

Sinking Carnivore Pellets. Hikari. (n.d.). https://www.hikariusa.com/tropical_folder/sinking_carnivore_pellets.html

Subbiahanadar Chelladurai, K., Selvan Christyraj, J.D., Azhagesan, A. et al. Exploring the effect of UV-C radiation on earthworm and understanding its genomic integrity in the context of H2AX expression. Sci Rep 10, 21005 (2020).

Themes, U. (2017, January 8). Reptile and amphibian nutrition. Veterian Key. https://veteriankey.com/reptile-and-amphibian-nutrition/

Whitaker, B. R., & Yaw, T. J. (2023, November 14). Noninfectious disorders of amphibians. Merck Veterinary Manual. https://www.merckvetmanual.com/exotic-and-laboratory-animals/amphibians/noninfectious-disorders-of-amphibians

Worm Bin Problems and Solutions. Worm Compost Puts Life Back in Your Soil and Health in Your Plants. (n.d.-b). https://www.sierra-worm-compost.com/worm-bin-problems.html

Worm identification PT 3-African nightcrawlers. The Blue Worm Bin. (2023). https://thebluewormbin.com/worm-identification-african-nightcrawlers/