When I set up my 20g I used a hot filter and pad I had from an older tank. When the water started flowing I noticed these really tiny worms, white with little heads and a longer filament type tail swimming about. Yikes.

Naturally, I am not going to put any fish in here until I figure this out and kill these worms or whatever they are. Frankly, they look a bit like pictures of sperm. I was going to do a fishless cycle on this tank and now I am thinking to really dose up to toxic levels for a few days. I'm talking about maybe 40 - 80 ppm in the hopes of killing these things.

Perhaps I should use bleach. Perhaps I should break it back down and sterilize everything and ReStart. Since there are no fish it seems that I could sterilize it without taking everything apart.

Does anyone know what these things are? They are nearly microscopic and that makes me unsure that I have killed all of them when I get ready to stock.

Edit to add: A little net surfing suggest these might be nematodes. This filter was never in a tank with fish. It was put on that 14 gallon plastic container I was going to use for my fry. It got a bunch of green water before it cycled and I just threw it out and got the 20g long.

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60g tall, all artificial plants, Rainbow tank; 55g for African Cichlids. 20g long for fry; 20g hex, 2 black Angels at my desk; 10g planted, with 50 Molly fry; 10 gal, 2x 13w cfl lightning, planted; 2g hex for "Buddy the Betta"; Wanting a 200g +, MTS getting bad.

They are quite common free living segmented worms that look much like Nematodes at first glance. They live on the excess food and waste left by the fish. Frequent water changes and some vacuuming of the gravel along with not over feeding will reduce these little free living worms swimming out of the dirty filter in the tank from where it came.

Charles H

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27 to 35 tanks from 5 to 55 gallon fresh water tanks. 300 to 350 gal in all.
Spawning mostly Killies, Live bearers, American & west African Cichlids, Pencil fish. 4 species of spawning Corydoras, & some Bristle nose Plecos. Other less than 6 inch species from time to time.

In St. Louis
Change As Much Water As Often As You Can

Well, this filter was never in a tank with either fish or food. I bought it new from petco and put it on that plastic container and started a fishless cycle. The only thing that went into that container was ammonia and light. I bought the gravel from petco as well and rinsed the living crap out of it. A real puzzle to me.

I just added salt, two teaspoons per gallon, therefore 40 spoons full and just shook it out all over the gravel. The tank is empty except for the gravel. I waited a few minutes and stirred the gravel with a stick. Now all I see are dead filaments floating around. I can see no living worms. I am going to let the salt soak the tank for a day or two then I am going to add another 40 teaspoons, wait an hour or so, stir the gravel then to a 90% wc, gravel cleaning. If I see any more worms I may add a pint of alcohol! What the heck, there's nothing in there and the alcohol will evaporate..

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60g tall, all artificial plants, Rainbow tank; 55g for African Cichlids. 20g long for fry; 20g hex, 2 black Angels at my desk; 10g planted, with 50 Molly fry; 10 gal, 2x 13w cfl lightning, planted; 2g hex for "Buddy the Betta"; Wanting a 200g +, MTS getting bad.

What does "hot filter" mean?

" When I set up my 20g I used a hot filter and pad I had from an older tank. When the water started flowing I noticed these really tiny worms, white with little heads and a longer filament type tail swimming about. Yikes."

If you used fish and plant free water, gravel, filter and glass cage - there is no way anything parasitic could be in the water. If the "Hot Filter" were from an old tank that was running, the filter could contain free living worms. If there were completely sterile ingredients used through out the setup, the worms could be larva of small insects that left eggs in the water to hatch.

All your trouble to kill off free living fish food is curious.

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27 to 35 tanks from 5 to 55 gallon fresh water tanks. 300 to 350 gal in all.
Spawning mostly Killies, Live bearers, American & west African Cichlids, Pencil fish. 4 species of spawning Corydoras, & some Bristle nose Plecos. Other less than 6 inch species from time to time.

In St. Louis
Change As Much Water As Often As You Can

HOT= Hang on Top filter. If I were 100% sure they were non-harmful I would let them live. I am not, so they will die. Some of these worm species are parasitic to fish and as I LOVE my fish I will not take the chance. I do not like to have organisms in my tank that I don't know what they are.

It is a puzzle regarding the source. As I said, the filter was never in a tank. Oh man, I just this moment remembered that I used a filter from my 10g to help jump start the fishless cycle. I'll bet that's where they came from. Now I've got to check the 10g gravel to see if they are there. I'll keep you posted.

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60g tall, all artificial plants, Rainbow tank; 55g for African Cichlids. 20g long for fry; 20g hex, 2 black Angels at my desk; 10g planted, with 50 Molly fry; 10 gal, 2x 13w cfl lightning, planted; 2g hex for "Buddy the Betta"; Wanting a 200g +, MTS getting bad.

Aquarium fish parasites have been a business and study of mine for 2 + decades. What you have introduced is free living and nothing but fish food.

Charles H

__________________
27 to 35 tanks from 5 to 55 gallon fresh water tanks. 300 to 350 gal in all.
Spawning mostly Killies, Live bearers, American & west African Cichlids, Pencil fish. 4 species of spawning Corydoras, & some Bristle nose Plecos. Other less than 6 inch species from time to time.

In St. Louis
Change As Much Water As Often As You Can

You maybe mean HOB filter= hang on back filter.

I think most healthy tanks are teeming with tiny life we don't even see most of the time but they help to keep the tank balanced.

It's just that when I can see worms, which have nasty reputation as parasites, that seems a clear and present danger, to steal a line. lol

"Aquarium fish parasites have been a business and study of mine for 2 + decades. What you have introduced is free living and nothing but fish food.

Charles H"

Charles, just so I know for future reference, what part of my description of the worms indicated that they were harmless? I have not studied them for twenty years so I was unsure.

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60g tall, all artificial plants, Rainbow tank; 55g for African Cichlids. 20g long for fry; 20g hex, 2 black Angels at my desk; 10g planted, with 50 Molly fry; 10 gal, 2x 13w cfl lightning, planted; 2g hex for "Buddy the Betta"; Wanting a 200g +, MTS getting bad.

Parasite Nematodes do not have the ability to store nourishment for days, they need to find a host quickly. Most free living worms are the same way, they need nourishment constantly. The filter has lots of stuff trapped in it that would be nourishment for them but not for parasitic Nematodes.

If the filter is dry now but came from a working tank, it could attract some small insects that could have left eggs in it. The worms could be larva of that insect.

Either way, just more live fish food.

Charles H

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27 to 35 tanks from 5 to 55 gallon fresh water tanks. 300 to 350 gal in all.
Spawning mostly Killies, Live bearers, American & west African Cichlids, Pencil fish. 4 species of spawning Corydoras, & some Bristle nose Plecos. Other less than 6 inch species from time to time.

In St. Louis
Change As Much Water As Often As You Can

Fill a jar of water and let it sit out with the top off for a couple weeks....
Something if not a lot will start growing in there.
Even if your set-up is new new new and rinsed, there can always be airborne or waterborne microscopic life introduced.
If this has happen to you during a set up cycle with no fish, the chances are it will happen again. But when fish are added you may never see it, cause they will eat it all.
Like inkmaker says.... It's not likely to be parasitic if there has been no host, so they will die off on there own.
You can also raise the temp. to 88+ and heat treat your tank wiping all nasties out.

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"Buddha in your tank"

The parasitic worms I know of enter the fish at egg or microscopic larvae so are unlikely to be seen free swimming with the naked eye .