Is this a parasite in my guppy? Should I treat the whole tank?

Question

A while ago I noticed a long white stringy thing hanging from my guppy's bum. He passed it so I ignored it. Now yesterday he passed another long stringy thing with a white thicker c shaped thing on the end. Is it a nematode parasite? None of the others have it (that I can see). He has been eating but today I noticed he looks thin. Im going to buy some medicine today.

Four questions:

1.Should I just treat the whole tank? I have 4 guppies.

2.What is the benefit of just quarantining him?

3.Is there any risk to the other fish if I treat the whole tank?

4.If I quaranitne him can I use water from the established tank to decrease stress?

Oh yeah and can this pass to humans?

I hope the store staff are helpful.

Answer 1

What you're describing sounds like a type of waste that does point to something internal, but it could just be a sign of poor digestion.  Thaw a pea and peel the shell off.  Feed the inside to him to clear his digestive track.

If this doesn't help, you should medicate.  

I would quarantine him.  Often, when an infected fish dies, the parasite will leave the body and infect a new fish.  So if you are dealing with parasites, it would be a smart idea to remove the fish.  

The label would probably say if there was a threat to the other fish if you were to medicate the entire tank, which I don't recommend.  The only benefit this could have is treating the fish for early signs of the illness, but you're also giving it a chance to spread if it hasn't already.  If you're sure it's a parasite, remove the infected fish and treat the tank he was in lightly.  That way, if there are any parasites left behind, you can wipe them out.

Definitely use water from the tank he's in now.  Having to acclimate to new water is unnecessary stress.  

You would have to know the type of parasite to determine if it passes to people.  I haven't heard of any that are in tropical fish.

Good luck!

Answer 2

1. Treat the entire tank.  Any internal parasites that are passed from the body will remain in the substrate for quite a time until the can infect other fish, and will need to be killed there.

2. There isn't really a benefit.

3. They will be a bit stressed from the treatment, but any parasites in the tank will also be killed.

4. Yes.

This will not pass to humans.  Remove any activated carbon from the filter and begin soaking the fishes' food in medication (metronidazole, praziquantel, etc.).  After the food has soaked, put the whole container, food, medicated tank water, and all into the tank-- the injested medicated food will go straight to the infection, while the medicated water will be absorbed into the fish and kill any free parasites.  Peas will do NOTHING for parasites or any infection!  The only use for peas is to remedy constipation, as it acts as a fairly gentle laxative.

EDIT: Definitely leave the filter in.  I suggested removing the activated carbon, but this is less necessary for pre-medicated food, as you aren't also adding a container full of liquid medicine.  Go ahead and leave the entire filter intact.