Aggressive Harlequin Rasboras

HI everyone. If anyone has any input or advice with this issue I'd be really grateful.

I had a 40 gallon and two 13g tanks.
The 13g each had 1 male Betta. The 40 gallon had 15 harlequin rasboras.
Unfortunately I had to sell the 40g, I just didn't have the time or money to keep up with all three tanks, I was really gutted but looking back I should've stuck with just the 1 13g, even 2 is a bit too time consuming for me!

The rasboras I split between the 13g tanks, 8 in one, 7 in the other. Both bettas are very laid back and docile and haven't once shown any aggression or unhappiness at the rasboras presence.

Two days ago, I noticed one of the rasboras had a half eaten tail. I immediately blamed the Betta, but I sat and watched the tank for half and hour, and I am 95% sure it was actually done by one of the rasboras. There has always been some little nips between them all, in the 40 gallon too, but the largest rasbora has become a tyrant and sticks to one spot and attacks any fish that comes near it.

When I woke up the next morning, the poor guy with half a tail, had had the rest bitten off.
I watched the other tank to see if there was similar behaviour, and noticed 2 of the rasboras in the other tank having what looked like a stand off.
They swam next to each other and wiggles their bodies so they were bashing each other with their tails, body slammed each other, and was nipping at the other ones bodies. It lasted a few minutes, and I haven't noticed then doing it again, but there is still some chasing and nipping. I've never seen anything like this before and I'm really concerned for all the fish now. I only want to do what's best for them.

I spoke to the pet shop I got them from and they told me its normal behaviour, establishing pecking order etc but it seems like much more than that especially as one has no tail, and a couple of them have little nips missing from the corners of their tails.
They also said they would not take the fish back.
I've tried advertising them for a new home, but no one wants them, and I'm completely stuck now on what to do.
I'm not sure why they are fighting, and don't know how to resolve the issue, in concerned they will start picking on the bettas, and as far as I know, this aggressive behaviour is unusual for this species, so there must be something that is affecting them.
I really like these little fish but I want them to be happy, and I don't want any of them to suffer.

Does anyone have any idea what I could do to help resolve the aggression issues? And also what to do for the guy with no tail?
He swims around fine but is not grouping with the rest of the fish, he's eating fine and I make sure they all get a good share (I hand feed the bettas so I know they're getting enough too).

Thanks.

 

Got a video of some of the behaviour. Not the best video and please excuse the noisy fan in the background.

It's the same two fish constantly fighting each other, and this is in the different tank to the one who had his tail
Bitten off!!

I've actually just seen them pick on Florian the betta, and I've not seen that before.
Think I may just have to take them to the shop in a bucket and tell them I'm leaving them there one way or another!

 

This is completely normal behaviour : two males showing off (the bigger one around is a female). I seriously doubt the fins are bitten of.
Are these hengelI ?

 

DoubleDutch, in the picture I posted you can see that the fish is missing his tail.
And I can see small corners bitten off the other ones tails. They are still going now, squaring up to each other and really attaching each other.

They are harlequins.

 

As said I think it is quite normal behaviour and seriously doubt they damage each other.
There are three species looking a bit the same trigonostigma heteromorpha, hengelI amd espei. They look a little small to be the "common" heteromorpha

 

But you can see in the first picture that he is missing his tail!
And I can't get pictures to show as they move too fast, but there are a few with noticeable bites out of their tail.
It's possible that it's Normal.. but it seems really viscious and they aren't giving up. And I have now just noticed a rip in Florians tail that wasn't there yesterday... and I'm concerned they will damage themselves/his fins more.

 

I just have to say, I had a school of harlequin rasboras for years and never once saw that kind of behavior. It looks out of character to me based on my experience with that fish....

 

Ok, I've got some more pics so I can try to show the tail damage a couple have..

Missing pretty much all of his tail



Missing a small nip from the top part of his tail - you can see it's a little shorter and not quite rounded



Missing small nips out of both parts of his tail. Not major damage, but you can see the raggedy ends



One with no tail damage, no jagged parts, both equal in length, rounded shape.

I hope that shows a bit better that some of them do have some fin damage. I know it's small, and the pictures aren't very clear (it's much easier to see in person) but it's definitely there.

As far as I am aware, they are Harlequin Rasboras. They were sold as Harlequins. But I am no pro so can't be 100%

 

I didn't say there is no damage, but I seriously doubt it is inflicted by the fish.

 

Oh sorry. What else could've caused it though? I've seen them nipping and chasing at each other.
There's no sharp ornaments or plants in the tank. Ammonia and nitrites are 0, nitrates are a little high as I have 40ppm in my tap water, but I'm using nitrate minus to try reduce that.

What else could be the cause of this damage? They didn't have it when I got them.

 

I noticed them picking on the Bettas, and that they bettas were not really coming out too much and hiding at the back of the tanks. So I went to the pet shop and told them I wanted to return or swap them, and they swapped them for some Corydoras for me.

 

My HR seem bigger and fatter. Could it be that they need more food?

 

I took these pics just before I fed them, the whole tank had been starved for a day as the Betta had bloat from eating the snail food! But the aggression had been going on well before and after that day. They were all fed well, as much food as they could eat in a few minutes, and until they all had a rounded pouch belly, and they had a range of flakes, pellets, granules and frozen food.

The last picture shows how they looked more often.
The shop took them back. I was quite sad to see them go, they were cute little fish, but they were bullying the bettas to the point they wouldn't come out from the back of the tank, and both now have a fair few tears and nips in the fins.

 

Okay. A shame younhad to bring them back. Stays quite weird

 

It was. They were really cute and fun to watch, but they were beating up themselves and the bettas too much, and it was stressing me out, so can't imagine how the poor fish were feeling.

I don't know why they were acting that way.. but I'm pretty sure it wasn't normal.

 

Of all fishes to be aggressive, harlequins would be one of the last I could imagine. But, it goes to show that anything is possible with certain fish in certain situations.

 

I also didn't think that they were aggressive fish. Not sure why they became that way xx