My guppies has some blood on their body

My guppies has some blood on their body. (I think is a disease not injury)What is this? What medicine should I use?

There is not enough info. to know what ur guppies have so0o0o it might be one of these:

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Toxins in the Water: The Invisible Culprit.

Fish will often jump out of a toxic environment.

HEAVY METALS such as copper, iron, zinc, and lead destroy the fish's slime coat, cause blood patches, cloudy eyes, listlessness, and damage the gills, leading to death. Keep all metal out of the tank. If you have problems you cannot identify you may be able to link them to contamination from old copper pipes. While copper is sometimes used to cure protozoal diseases the concentration used is relatively safe. When treating fish with copper make sure your water conditioner does not deactivate heavy metals or it will have no effect.

OTHER TOXINS include chlorine, chloramines, chemical sprays used in the home, tobacco (via fumes or from fingernails put in the water), paint fumes, ammonia, unsuitable plastic decorations (don't use it if it smells strongly of plastic), or dead snails, which will quickly pollute an aquarium and kill the fish.

If you suspect toxins, carry out a 50% water change immediately and find the source of the trouble.

There are many diseases and parasites that can attack a Guppy. Here I will attempt to explain some of the most common ones guppies experience.

EXTERNAL PARASITES!