Molly Biting Platy's Tail?

[MaryBee]

I have a 30L tank and only two mollys and a platy. The white molly is quite aggresive and the platy has taken to spending most of the time in a tall green plant, comes out occasionally and at feeding time; this morning I noticed he had a little bit missing from his tailfin and I wondered if the molly had taken a chunk out of it. He chases the other molly out of the way too when it is feeding time but that one is still quite active. Any ideas please.

 

[fluttermoth]

I'm afraid once a fish starts picking on another fish, there's very rarely anything you can do, apart from separating them.

It can sometimes help to add more fish, to spread the aggression around, but you don't have room for any more fish in your tank.

 

[Fish Lover Forever]

I would recommend getting treatment for rotfin because my guppy did that to my mickey mouse platy and we put the treatment in too late.


Mickey Mouse

There is a chance the same thing will happen !

 

[MaryBee]

Since posting yesterday, another big chunk has disappeared from the platy's tail. I'm not sure that it is the molly doing it, now.

The damage to the top of the tail happened overnight on Wednesday night, and the damage to the bottom happened some time during the daytime on Thursday. Does anybody have any idea what might have caused this?

 

[Fish Lover Forever]

Well it does need treatment because that looks bad to me and definetly is not mild. My advice is to show the photo to a fish shop and they will give you the right treatment before it is too late. I would say that that is rotfin. It is a bacterial disease so it can be caused by poor water conditions. If you do not already have one I would suggest getting a test kit and testing the water and then if there is something wrong with your water you will know and you will be able to fix it.

 

[fluttermoth]

That doesn't look like fin rot to me, although that could develop later, as secondary infection if water quality isn't kept high.

It looks like nipping, and there's probably nothing you can do to prevent it, apart from separating the fish, or getting bigger tank and adding some more (I would say a 30l tank is way too small for mollies anyway).

 

[MaryBee]

Thank you for your replies. Fish Expert Forever, I see that you sent me a private message, but unfortunately the Forum software says that I'm not allowed to use the private messaging system.

fluttermoth, the mollies were recommended by the sales assistant that sold me the aquarium. I was hoping to get a few more fish; do you think that I shouldn't?

I've had the aquarium since 9th September. I use Tetra Aqua Safe, Tetra Safe Start, and King British Green Algae Control. I do a 30% water change and rinse the filter once a week, and test the water about twice a week. Our GH is always high (500 mg/l) and pH is about 8. Nitrates seem to spike a little after a water change/filter rinse (between 10 and 25 mg/l) but fall a couple of days later.

 

[fluttermoth]

Definitely don't get any more fish for that tank. Mollies should grow quite large (around four/five inches) if they have the room. I personally wouldn't keep them in anything smaller than a two foot/60l tank.

I'm afraid most shops will be happy to sell people unsuitable fish; they're there to make a profit, and if they can sell you more fish than your tank will hold, then that's more money in their pocket

 

[Katelite]

I was recommended to get Molly's as there not aggressive apparently, exactly the same thing happened to me!!
My Molly's killed two guppies and two cardinals, chasing them around the tank and taking chunks out of there tails just like your pic. I took the back to the aquarium! If you leave them in there with your other fish they will kill it!

 

[Tuxyu3]

Somebody more experienced with them feel free to correct me if i am wrong but i do believe mollies are usually only ever aggressive if they are kept in unsuitable conditions.

 

[Fish Lover Forever]

Somebody more experienced with them feel free to correct me if i am wrong but i do believe mollies are usually only ever aggressive if they are kept in unsuitable conditions.

Yes, this is right. I have a dalmation molly and he does like to play about and chase the guppies sometimes but he has never done any harm to them.