About one week ago, I treated my fish with some blackworms bought from LFS. When I dropped the worms, some of them hided themselves in the gravels. I thought after some hours they will die so I did not do anything to drive them out.

Yesterday night, I found some blackworms moving out from the gravels, they are living well in the gravels!!! Also I found a lot of tiny, white worms in the gravels, which should be the generated these blackworms. I believe in no time the substrate will be full of blackworms.

I am wondering whether the blackworms will do harm to my plant and my tank?
If so, I have to get them out. But how can I get them out? The blackworms only moves out in the black, when the fish are all sleeping and can not eat them. Any suggestion about this is appreciated!

well, at least your catfish will be happy if you have any.....think of those worms as having more fish. they are going to use up oxygen and create waste. do not, if at all possible, help to keep them alive. your tank could become a mess. I would try to siphon them out.

Good luck!

But they are buried in the sand so that it is impossible to siphon them out. I am wondering whether there are some medincine to kill them and do not harm my fish or whether there are some fish that forage at night. I need small fish for I already have a lot of fish in my 20 Gal tank.

It is really strange that this blackworms can survive in my tank. Articles talking about live food always said that the worms will survive in a freshwater tank for a couple of hours, but the worms in my tank seem to be strong and productive.

do you have any catfish? cories? one that would be real good are kuhlii loaches. they bury themselves in the substate. all would be active at night.

you mean all the cories and loaches are active at night?

typically, and i do stress typically, catfish are nocturnal.

It is hard to find the kuhlii loaches in LFS now. And my substrate consists of a layer of sand and another layer of gravels above. So it will be hard for any fish to bury itself into the substrate. So I have to find some fast-swimming and active fish to catch the worms when they are moving out from the gravels.

And I am wondering is there any medicines that can kill these worms and be safe to my fish. Does the ich medicine (containing the copper) kill worms, I know it can kill shrimps, snails or other invertibrate, but I am not sure the worms are hardy enough or not to survive.

I don't think there is any reason to get concerned. The worms are probably eating the leftover food and decaying plant matter in your substrate. I doubt they are herbaceous. There may be a chemical solution but I wouldn't recommend it. It's one thing to have a 100 worms exceeding waste, and it's another to have 100 decaying worms fouling the water. One thing you may want to try is to cut down of feeding your fish. Let them get hungry so they will forage for food instead of waiting for you to deliver. Search some of the fish profiles there should be a number of nocturnal fish that can help you out. The yoyo loach comes to mind.

it probably would, but be careful with that stuff. some of your plants may also be very sensitive to the copper.

I feel strongly that they're not herbivorous. But I doubt they're herbaceous, as well.

i've been able to culture them, but I would not allow more than a few to live in a display tank at one time. They produce lots of nitrates...if they suddenly decide to die...so much the better.


Most fish can eat blackworms even if they are buried. They don't stay buried, as they must protrude there bodies for extra O2. Even puny heterandria formosa can successfully grab and either rip apart or pull or worm from the substrate.

In another thread in the Fish section, I mentioned how good Tiger Barbs are at ripping these worms from the substrate. So are Bettas.

Once they are in the substrate, you are stuck with them. Luckily, as has been said, their tails protrude into the water column to aid in breathing. That gives fish a chance to see them, but only the fastest, stealthiest fish will catch them before they pull back down below the surface. Cories and loaches can easily dig them out.

Like any creature, they will survive only if there is a enough to eat, so if you are not overfeeding, only a few will live -- and will not cause any harm to fish or plants.

What may surprise you, and what you should be more concerned with, are the "other" creatures that come with the blackworms, specifically those small, grayish oval-shaped flat worms that are present in every batch of blackworms I have bought.

I noticed a quarter-inch specimen perched on some driftwood after a feeding and ignored it, assuming he would be eaten. Well, months later, this quarter-inch gray worm had grown into a 5-inch pink worm and gave me quite a shock when I was uprooting some plants during a cleaning. I recall thinking, "hey, there's my khuli loach," and then remembered that I do not have a khulie loach . This thing darted away and disappeared into a bunch of wisteria, where I could not find him. A few weeks later, I noticed "something" poking above the substrate and after a minute or so of poking and digging with a fork, I hauled this scary monstrosity out of the tank.

It was a good 5 inches long, yet could contract itself down to about an inch and a half. It was also very tough, as if made of leather, and resisted my attempts to cut it in half with the edge of the fork. I was prepared to rinse it down the sink drain when I noticed the salt shaker... It reacted just as a slug would.

Thanks for all replies.
After introduing three cories and digging out some worms, there is no noticeable trace of black worms.
I really see the small, grayish oval-shaped flat worms when feeding and I pick them out. But I still find one tiny, similar shape, white worm moving in gravels. Maybe it is brought into the tank by eggs. Hopefully it will not grow to a big one.

funny and scary all at the same time. yeah, i remember seeing stuff like in packs of live bloodworms that we used to get. that stuff can be scary!