Whitish-cottony-hairy stuff may be fungus or bacterial.
Fungus often move in on compromised tissue. Some other problem started, then the fungus started growing.
Bacterial might be something like Columnaris, but I suggest you do more research and look at pictures of this disease.
At the current time, without knowing the problem it is impossible to name a medication.
Treatment would be aimed at reducing the number of pathogens in the tank, and optimizing the water parameters for the fish. Lots of water changes with good filter maintenance and vacuuming the floor of the tank.
Make sure the temperature is optimum for the fish (Zebra Danios prefer cooler water than many tropical fish). Fairly soft water, pH about neutral or somewhat lower.
The torn fins can be from any of at least 3 problems, or perhaps something else.
1) During the chase and capture, the tails got torn.
2) Fin rot can soften the tissue so the fins (tail fins or other fins) can split. Fin rot can be caused by any of several bacterial diseases.
3) Zebra Danios can chase and nip each other, and can do damage like that.
Once the fins are torn fungus can start growing on the damaged tissue.
Fungus often move in on compromised tissue. Some other problem started, then the fungus started growing.
Bacterial might be something like Columnaris, but I suggest you do more research and look at pictures of this disease.
At the current time, without knowing the problem it is impossible to name a medication.
Treatment would be aimed at reducing the number of pathogens in the tank, and optimizing the water parameters for the fish. Lots of water changes with good filter maintenance and vacuuming the floor of the tank.
Make sure the temperature is optimum for the fish (Zebra Danios prefer cooler water than many tropical fish). Fairly soft water, pH about neutral or somewhat lower.
The torn fins can be from any of at least 3 problems, or perhaps something else.
1) During the chase and capture, the tails got torn.
2) Fin rot can soften the tissue so the fins (tail fins or other fins) can split. Fin rot can be caused by any of several bacterial diseases.
3) Zebra Danios can chase and nip each other, and can do damage like that.
Once the fins are torn fungus can start growing on the damaged tissue.
