Hi new to tropical fish keeping

[Shellyedwards83]

hi I have a new tank and have a a few fish I have 4 tetra 8 guppies mixed sex a Siamese fighter male and 3 mollys and my male guppies fins seem to be disappearing and I'm worried is this fin rot or could something be nipping at them I'm gutted they were beautiful

 

[Munroco]

Nipping I'd say. Bettas are notorius for nipping guppies fins. Some tetras aren't averse to taking a chunk out of these flowing tails either. What kind of tetras?

 

[topazshadowwalker]

The Siamese fighter is most likely your culprit, but as also said tetras can be pains for nipping too, personally would not keep fighters with fish with flowing fins