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i have been feeding cories black worms for years. has anyone ever had an episode where they put in the black worms and:
* they start to die and turn white within 2 or 3 hours * and a white film starts to build underneath them on the bottom of the tank.

the worms are fine in the same water in the fridge.

i added formalin 3 prior to putting in the cories. would that do it? anyone ever experience this.
what could be in the water to do that?

thanks

Black worms are very sensitive to many fish medications and formalin is among the most acutely toxic chemical you could use to kill perfectly healthy black worms quickly.
Once dead, black worms quickly rot in your aquarium and present a very real danger to your fish.
Black worms normally tolerate malachite green used for Ich, most antibiotics and oddly it may seem, anti-worm parasite medications but that is because not all worms belong to the same taxonomic classes. Black worms also tolerate metronidazole.
Formalin and copper sulfate are 2 commonly used chemicals which black worms can not tolerate.

Just wondering, what exactly are blackworms? Are they the larval forms of insects (like bloodworms) or are they 'worms' in their own right?

Would be grateful if you (an unspecified person) could also write up what you believe might be necessary for their care...

Thanks!

Black worms, Lumbriculus variegatus, are an aquatic relative of the common earthworm, Lumbricus terrestris.
They are commercially raised as a live fish food for the tropical fish hobby and are also widely used by governmental game fish hatcheries. Here is a little basic info:
http://www.ehow.com/how_4784258_keep-ca ... ridge.html
There are several major suppliers on the West and East Coasts who ship them over night to your door step.
Many fish shops carry and sell black worms in smaller portions.
They are extremely useful as a catfish breeder conditioning food and are widely used by Discus keepers/breeders.
I use them for my carnivorous plecos, Discus and Apistogramma. I use one to two pounds a week and usually buy 3 lbs a week. I have a fish friend who takes one pound which saves us freight costs per pound. The larger quantity you can buy the lower the unit cost. It costs as much to ship one pound as it does 3 three pounds.

thanks for your quick reply. I thought that the formalin would have something to do with.
boy o'l boy did it kill them quickly. i would say with in an hr. good thing i checked because i syphoned the water as soon as i saw it.

Quick action was probably a life saver. Few thing go rank faster than dead blackworms.

Here is more compreshensive information about cultured blackworms and the questions of their safety visa vi transmission of fish parasites or rather, the lack thereof.
http://www.simplydiscus.com/library/foo ... ndex.shtml
Discus hobbyists, perhaps more so than most other tropical fish keepers have many baseless anxieties over the safety of live foods than any other group of specialty aquarists I know so this info from the popular US Discus forum, http://www.simplydiscus.com is particularly relevant.
It's true I pick at many Discus keepers' perennial myths about keeping and breeding Discus but I began breeding wild Discus in 1969 so I have been involved with them a long time and have raised and sold 1000's of them. I am a self taught Discus breeder. Back when I began most of the work on breeding new domestic strains was being carried out in Germany. The famous Jack Wattley was among the first to begin developing domestic color strains in the USA using the best wild fish he collected and bought in South America and sharing stock with the father of the fancy hybrid Discus strains. Dr. Eduard Schmidt-Focke. To his credit, simplydiscus.com owner, Al Sabetta, took the time to learn then present the facts about using California Blackworms as a tropical fish food. Regardless of where you buy your blackworms they are all raised in California. Note that regardless of where you buy your live blackworms they will only be as good as they are stored and purchased soon after they become available. Since blackworms are kept unfed and refrigerated their nutritional value declines over every passing day. Once any begin dying the entire lot becomes unsuitable food and should not be used under any circumstances.

Wow, thanks a lot! Well appreciated.

I just want to emphasize this:

apistomaster wrote:Once any begin dying the entire lot becomes unsuitable food and should not be used under any circumstances.

Rotten food is an extremely efficient way to kill your fish. Never ever feed your fish foodstuffs which have started to spoil.

This isn't restricted to blackworms, of course, but applies equally to other "wet" foods, especially frozen foods.

i dont like using live black worms
jsut because of the fact they are sensitive
i get dryed black worms and squeeeze them in a cup of tank water so they will sink
some times my cory even go to the surface to eat the floating ones