Guppy's tail ripping with thin threads coming out

Hi all,

I've just recently become interested in keeping fish (most specifically guppies). My father has a few, but recently, I've noticed that a lot of the tails of the male guppies are ripping and thin threads are coming out of the tails. Only the males seem to be affected, the female seems fine. I did move them from a smaller tank to a larger tank a couple days ago. Also, all of the guppies seem to be swimming with their heads right under the surface of the water. Is this normal? Could somebody please help me out?

It doesn’t really look like fin rot. What other fish are in the tank? Any decor he can catch it in? What is the size and water parameters of your tank?

There were 5 angelfish, of which 2 are very territorial. The other 3 are pretty peaceful but I'd already separated the 2 aggressive ones. I don't know if it's the angelfish nipping them though because they used to be in the same tank for quite a long time and there were no problems until now. The tanks is able 55 gallons (120cmx50cmx35cm)

I would suspect the angels.
Also FWIW 3 angels in a 55G usually results in one angel surviving. And if the 2 you removed are not a bonded pair only the strongest of those will survive.

The two separated angelfish are a bonded pair. They get especially territorial when they have eggs so I separated them. They're still in the same tank though, I just placed a partition in between. Should I separate the angels then?

Hi and welcome to the forum

How long has the tank been set up for?
How long have you had the fish for?

How often do you do water changes and how much do you change?
Do you gravel clean the tank when you do a water change?
Do you dechlorinate the new water before adding it to the tank?

What is the ammonia, nitrite, nitrate, pH and GH of the tank water?
What sort of filter do you have?
How often and how do you clean the filter?

Have you added anything new (fish, plants, wood, etc) to the tank in the 2 weeks before this started?
Do you add plant fertilisers, supplements or anything else to the tank?

Are there any other fishes in the tank besides the angelfish and guppies?

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Right now you should test the water quality for ammonia, nitrite, nitrate, pH and GH and post the results (in numbers) here. If you don't have test kits, take a glass full of tank water to the local pet shop and ask them if they can test it for you. Write the results down in numbers when they do the tests. If they say "The water is fine", ask them what the results are in numbers.

Wipe the inside of the glass down with a clean fish sponge.

Clean the filter if it hasn't been done in the last 2 weeks. However, do not clean the filter if it is less than 6 weeks old because you can wash out the filter bacteria and start the cycling process again.

Do a 75% water change and gravel clean the substrate every day for at least one week or until the problem is identified or resolved.

Increase aeration/ surface turbulence to maximise the oxygen levels in the water.

Hi and thanks for the welcome. The threads seem to have disappeared now, even though I haven't done anything extra. I will check the water, thanks for that advice. Other than angelfish, the only other fish are catfish. Most of them a bristlenose catfish, a couple other I'm not sure exactly of the species, but they look very similar to the bristlenose except that they have much less bristles and much longer fins. I will do a water change in a couple days.