Q: SN wrote,

Dear Nippyfish,
Are live black worms safe to feed to my betta or could they cause a parasitic infestation? If they are safe, what is the best way to keep them alive and how many should I feed at a time? Should I feed them only as a treat?

A: In my opinion black worms are a terrific addition to a betta’s diet. Some aquarists, however, fear that they will introduce parasites or bacteria to their tanks. With any live food, there is some risk of infecting your fish with bad bugs but often the rewards far outweigh the risks. I recommend only buying the worms from a store you trust but even this doesn’t insure complete safety.

I fed black worms several times a week to my bettas, dwarf puffers, dwarf gouramis, danios and African dwarf frogs up until last year when I moved and they were no longer available in my area. For the couple of years I used them as a major staple in their diets and I found that my fish were of a healthier weight and color and they fell ill far less often. I can’t say for certain if the black worms deserve all the credit for my healthy fish, but I am certain they didn’t cause any harm. The talk about live foods being “too rich” for bettas, I suspect, is a product of internet advice gone wild. One person says it’s too rich in some online forum without any real explanation of what that even means and the next thing you know everyone is scarred to feed bettas what they would eat naturally in the wild. You can read more about feeding live foods in my article called Breaking the Rich Food Myth.

Because it is possible for black worms to harbor parasites and bacteria you should make an effort to keep your black worms in good condition. Black worms breathe air from the atmosphere and will drown if you keep them in containers filled too high with water. Keep them in a container (Gladware works well) and fill it with only about a 1/4 inch of water and poke tiny holes in the lid to allow for air exchange. I say “tiny holes” because the worms will crawl up the sides and you don’t want them squirming out. That would be gross. Then, to insure they will survive a long time, place them in the refrigerator. Yes, that’s right I said the refrigerator. By some miracle of God my significant other doesn’t seem to be bothered by this. I just converted the former veggie drawer to a fish food only space. If your family doesn’t fully appreciate your aqua-hobby you might need your own mini-fridge or at the very least find a cool garage or basement for black worm storage. They survive noticeably longer when kept cold.

Each day you should thoroughly rinse your black worms with cold water and remove any dead or nearly dead worms. It’s common for dead worms to float to the surface as you rinse, which makes their removal fairly easy. Now some people say you should only rinse them in conditioned water absent of chlorine and chloramines. My fish store guy told me he tried rinsing his in conditioned water and the whole shipment died. So which way is better? I have no idea. I have only rinsed and stored my black worms in tap water without the use of any conditioners. I like it because it’s easy.

It is not necessary to feed your black worms. Feeding is actually discouraged because the water will quickly foul and the worms will die from the toxins. It is normal for your black worms to get thinner over time. I usually buy a tablespoon full which lasts several fish about 3 weeks and I always run out before they die off naturally. I recommend buying the smallest quantity your fish store allows at first so you can determine how often you need to replenish them.

You will probably find that your betta loves black worms and will eat as many as you allow. To avoid complications with overfeeding, I like to offer only 4 – 5 black worms per day either split up into two feedings with something else or alone as one feeding. Just be sure to offer other foods as well to insure a balanced diet. If a worm gets by your betta don’t worry. It will hunker down into your substrate and can live for quite some time… well, until your betta hunts it down. Enjoy watching your betta stalk it’s prey. It’s a lot of fun to observe your fish demonstrate it’s natural instincts.

To learn more about feeding bettas in general visit the Feeding page at Nippyfish.net.

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Reader Interactions


  1. Ken says:

    I’ve been feeding my Bettas blackworms for over 5yrs now and it made a huge difference in size and color. That is true that people are scared of diseases and parasite in the worms but I never had a trouble of them getting sick. Feeding Blackworms to Bettas (but don’t forget your daily pellets for nutritional needs) in my opinion is a must for me cause they made my Bettas true to it’s self colors are brighter and scales are thicker with lots of sparing action


    I agree with you wholeheartedly in regards to the benefits of black worms, but couldn’t disagree with you more regarding the care of your black worms. I’ve had a 10 gallon tank set up just for black worms for quite some time. That said, I can say with absolute certainty that they will not drown if they are kept in their natural state (submerged). If you line the bottom of your (black worm) tank with a thin layer of gravel they will continue to multiply for you indefinitely. They do require decent water quality, but I’ve found that a small sponge filter and an air stone keeps them quite happy. They also need to be fed. Dried oak leaves from last fall will work. This is especially helpful if you also need some infusoria. I usually throw in an algae wafer or a small pinch of flake food every few days. To harvest black worms I vacuum a different section of the tank every few days, running the output of my hose through a fine mesh net to collect the worms. I usually pull out about a gallon of water out of the tank while I’m doing this as it also servers as a regular water change.

    Recently I had to find a new home for my betta and the black worm tank was the only thing I had open. There is a much more interesting fish now that it’s hunting its own food and not being fed. I was initially worried that it would over eat, but that has not happened. Since that tank was really bare I took a cutting off my wife’s pothos plant and stuck it into the back of the tank. It didn’t take long before there was a really nice root mat at the top of the tank that the betta loves to hang out in. That tank now has pristine water quality and gives the betta a lot more of a natural habitat to live in.

    • Vice says:

      Had a question I just bought a tsp of black worms the lady at the store said I could just drop them in and they’d live in the substrate I wasn’t sure if I should do this but from what you’ve written I guess it ok would you suggest I do the same?5 gal two Amazon swords ,Marimo moss ball ,and a betta.

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