Yes, Sakura Thanks so much for sharing that information, I was recently looking into buying the Frozen Bloodworms for our Sammy, and came upon BlackWorms, and was wondering if ok, (I didnt order them) was unsure in either case, tried the Freeze dried ones, that's a no go, and also heard they expand which can cause bloat.
But will be sure to stay away..just in case. Very sorry about Train:((huggs))
So here are a few things I've learned about black worms.
According to The Betta Handbook by Robert J Goldstein, they are found in raceways at trout farms and in the effluent treatment ponds of vegetable processors in California. I don't know if they are found outside of California or not. They can't live for long in their own pollutants so if you plan on feeding black worms, you must rinse them in cold, dechlorinated water each day. If the water doesn't run clear or they don't tangle into a ball, throw them out.
Like tubifex worms, which are found in sewers and wastewater, black worms have a high risk of transmitting parasites to your fish. A good way to avoid this is to rinse the worms as noted. This purges them.
I would highly suggest cutting the worms into small pieces to avoid the possibility of them surviving ingestion and tearing the stomach of your betta. Feed only 1-2 worms at a time to avoid the engorging that happened to Train (little glutton snatched 4-6 of them off the net while I was trying to get the worms off).
I keep my blackworms in a small container with a sponge filter going in my room. I change their water daily using aged water from my goldfish tank and feed them fish flakes and old Indian Almond leaves.
I always rinse my blackworms after I bring them home from the store as some stores house them in disgusting conditions.
If they start looking poorly I chuck the whole lot out as I don't want to spread anything to my fish.
Other than that a good feed of blackworms never fails to incite spawning with my bettas, killies and natives.
If you do feed blackworms, I would advise keeping on the health of your fish, and worm your fish every few months just in case something slips past.