Betta And Male Guppies Suddenly Have Their Fins Ripped Up?

[LicianDragon]

I noticed this morning that my male betta and several of my male guppies have their tail fins torn up pretty badly. This all seemed to happen overnight. I have a 20 gallon tropical community tank.My fish include-
 
7 Fancy guppies:mixture males and females( Poecilia reticulata ) 
1 Golddust molly:female ( Poecilia sphenops )
1 Redtiger platy:male ( Xiphophorus maculatus )
2 julii cory cats (Corydoras julii) 
1 Peacock gudgeon female (Tateurndina ocellicauda)
1 Halfbeak (Dermogenys pusilla)
1 neon blue goby (Stiphodon atropurpureus)
2 Weather loaches (Misgurnus anguillicaudatus)
2 african dwarf frogs(Hymenochirus boettgeri)
1 betta, male( Betta splendens)
 
None of my fish ever show any aggression to each other, including the betta. He occasionally chases the male platy but he gives up almost immediately and he has never hurt any of my fish. (plus his fins are also torn up) As far as I know there is nothing else in my tank that would tear up the fins of my fish like this. Anyone have any ideas what happened?

 

[Chad]

Betta and guppy are two fish that should not be in the same tank with each other. Any fish with long fins is a target. The tail damage is likely from these fish fighting with one another.
Sometimes fish can go a while without showing aggression but as they age, go into mating cycle, etc. they can become aggressive.

 

[attibones]

I agree with the above. With so many fish in this tank, your betta may have very few places to hide. They like to have access to seclusion, you know. You ought to have more corydoras, no guppies or weather loaches. These particular loaches get up to ten inches long. With poor stocking, your fish will be stressed, which means more potential for aggression.

 

[This Old Spouse]

+1 Definitely agree. I think you should get a tank to house the betta by himself, otherwise you're going to end up with some dead fish. Loaches should also be rehomed. Corydoras should be in groups of at least 6. As for all those other fish, I'd do some careful research and planning for them.

 

[Plecc]

Isnt a neon blue goby a salt water fish?
 
 

 

[attibones]

Isnt a neon blue goby a salt water fish?
 
 

Indeed, there is a saltwater neon blue goby, but I believe this species is tropical. Finding mixed results.

 

[ReiRei]

Yeah, Bettas and Guppies are a big no no in the same tank - despite what shops say.

 

[the_lock_man]

More than likely it's the betta fighting with the guppies, especially if one of the guppies to it into its head to bite the betta's fins.
 
Possible alternative could be the molly, or the halfbeak.

 

[This Old Spouse]

Yikes, could be anything in that wild combination!

 

[Chad]

@LicianDragon I hope that answers your question. The good thing is that a Betta can be housed in a smaller tank like a 3-5 gallon (I prefer 5) so the trouble of re-homing it and the expense is minimal.

 

[kimbo182]

I've been having the same issue with my guppies & beta. I've had to seperate mine as the beta has destroyed my guppies fins over the space of 2 nights. Such a shame!

 

[LicianDragon]

This set-up has worked for 6 months without any issues. There has never been any aggression from my fish towards each other. The damage seemed to happen overnight, when I know the guppies and betta are asleep(turning the room light on in the middle of the night reveals them laying on the tank bottom or within the plants). Could the dwarf frogs be picking at them? Or the weather loaches?(also, I understand the weather loaches will outgrow the tank, they will moved to a bigger tank when needed. Currently they are only 3 inches).
I'm still not observing any aggressive behavior from and of my fish,

 

[N0body Of The Goat]

My top suspects would be the Betta, Platy, or Molly.

 

[ReiRei]

It might have worked for that long, but I strongly advise you to reconsider having guppies and a Berta in the same tank. Pet shops will say its fine (usually just to sell the fish) but actually its a prime cause of nipped fins

 

[Chad]

This set-up has worked for 6 months without any issues. There has never been any aggression from my fish towards each other.

 
This is quite common. However, if you are sure aggression is not the issue then my second thought would be fit rot disease.