Why my black molly fish is reacting like this ?

[ziadc]

This fish has no work in my aquarium except running behind my Goldfish an my 2 koi fishes and picking them ? Why he's acting like this ?

[Northernguy]

What is the temp of the tank?
Mollies and gold fish are not a very good combonation.The goldfish are probably picking on the mollie.

[Mvjnz]

Mollies love to nip at fins too, so should not be kept with fish big long/big fins.

[AmazingH]

Also, mollies are a tropical/slightly brackish fish.
Goldfish are coldwater.

Goldfish are usually huge next to a mollie...

[Chloeheartsfish]

Mollies love the slimecoat of goldfish, and will keep picking away at it until it dies. And also, yes, mollies are brackish tropicals, and goldfish are fresh cool water fish. And once the goldfish get big enough, they will eat the molly. the koi will get so huge eventually that they will definitely eat the molly.

[Wild Turkey]

Yup, they are eating the slime coat off the goldfish and it will eventually lead to ill effects that can kill the goldfish, i would adjust your stocking arrangements asap. Make sure you research before you buy in the future and you can avoid 99% of problems like this one

[ziadc]

I've isolated the molly in separate glass vase I'll soon put some small fish with it, i don't know what kind of fish can live with the molly ! maybe female molly ?

[Wild Turkey]

They prefer a little salt in the water and there are some other livebearing species that do also that make good tank mates.

I hope the vase is very temporary, hes not gonna last very long in there without a heater and a filter in an uncycled vase.

[Northernguy]

They prefer a little salt in the water and there are some other livebearing species that do also that make good tank mates.

I hope the vase is very temporary, hes not gonna last very long in there without a heater and a filter in an uncycled vase.

I agree! They need heated filtered water in a cycled tank or they won't lst long.