Harlequin Rasbora Bullying

FishForums.net Pet of the Month
🐶 POTM Poll is Open! 🦎 Click here to Vote! 🐰

ostnip

New Member
Joined
Nov 27, 2017
Messages
4
Reaction score
0
Ammonia: 0
Nitrite: 0
Nitrate <5
pH: 6.8
Temp: 78
I have a planted, cycled, and heated 20 gallon long that is currently housing one male betta, four cory catfish, and one harlequin rasbora. Around March of this year I bought 8 harlequin rasboras and I noticed an odd behavior in them. One rasbora would always be excluded from the group, pale and stressed and just hanging in the corner. This would go on until that rasbora would die and then the same thing would happen to another single rasbora. A few days before they die/disappear I would notice injuries on them and I would see the poor guy get chased around.

Eventually I got down to 4 of them so I bought more to bring the number back up to ten. Same thing happened. One of the bullied ones had this weird cyst and what looked like fungus coming out of the gills. I separated him but I believe this happened because of the stress of being bullied. Two different bettas have been in the tank and both never bothered the rasboras. The first betta that was in that tank passed away from dropsy symptoms but had the same fuzz the rasbora had a few days before passing away. So the bullying is dangerous to my other fish and I don't want the same thing to happen to the current betta in there.

The tank is pretty well planted so they have access to cover but rarely use it. For about a month I had two left until a few days ago where I noticed one of them was bleeding from his side. I tried to help him out and put peroxide on it but he passed away last night. Does anyone know why this is happening?
 

Attachments

  • 20171127_132023.jpg
    20171127_132023.jpg
    235.6 KB · Views: 975
weird, my grandma had the same thing happen. it was because of ich. from what i’ve noticed, the rasboras kicked out the diseased fish and bullied him until he died. this would pass the disease to the other fish and then the same cycle would happen again until they all died. I have had fish fungus once, and the two things that helped me were malafix, my favorite treatment for certain diseases, and salt for treating aquarium diseases. another salt that worked for me was kirkland brand natural sea salt, from costco.
 
weird, my grandma had the same thing happen. it was because of ich. from what i’ve noticed, the rasboras kicked out the diseased fish and bullied him until he died. this would pass the disease to the other fish and then the same cycle would happen again until they all died. I have had fish fungus once, and the two things that helped me were malafix, my favorite treatment for certain diseases, and salt for treating aquarium diseases. another salt that worked for me was kirkland brand natural sea salt, from costco.
Super weird. This fungus only appeared on about two of the rasboras 5 months ago and then I never saw it again. I might replace them with pencilfish if I can find them, but I'm really disappointed. Rasboras are found in the same waters as bettas and I wanted to keep the fish selection a little more natural but it just isn't working out.
 
You do not want pencilfish in with a Betta. Male bettas are not community fish and should be on their own. I realize you may have thought things were fine with the rasbora, and from that aspect they may or may not (the stress the Betta can cause other fish even without any actual physical aggression is still significant). But pencilfish are very different from rasbora, and I can almost guarantee they will enjoy nipping the flowing fins. And their persistence could well annoy the Betta to the degree that he goes after them.
 
You do not want pencilfish in with a Betta. Male bettas are not community fish and should be on their own. I realize you may have thought things were fine with the rasbora, and from that aspect they may or may not (the stress the Betta can cause other fish even without any actual physical aggression is still significant). But pencilfish are very different from rasbora, and I can almost guarantee they will enjoy nipping the flowing fins. And their persistence could well annoy the Betta to the degree that he goes after them.
I think whether or not bettas can be community fish is a matter of opinion and preference. In my opinion they can as long as the betta has the proper temperament and the community fish don't pester him. The rasboras and the betta didn't interact at all but I agree the rasboras could have been stressed by the betta's presence. I might just not add schooling fish, although I really want to, but if it's not gonna work out there's no point. I will be keeping the cories because they definitely do not interact with this betta and they do fine together.

I was suggested pencilfish because they are supposedly peaceful and prefer soft water like bettas do. The betta in the tank is a plakat so the likelihood of him getting nipped isn't as great but I know it can still happen. Before I had the rasboras, I had neon tetras and they nipped my late betta's fins so bad even though he was a plakat as well. The rasboras would have been fine if they wouldn't have killed each other. In the wild I don't think bettas would be the only fish in the stream/paddy. So they wouldn't be completely alone and unexposed to other fish their whole life which is why I thought rasboras would be a good, natural option.
 
I once had a female PK in a tank with Hengeli Rasboras till madam decided enough was enough and started killing them, I also had a male crown tail that killed a 2 inch BN pleco, I saw him do it, Even Malaysian Trumpet snails are not safe around Bettas.

Watch the white girl.
 
Last edited:
I see you are a new member, so welcome to TFF (didn't notice this previously). And as a new member, I will take the time to respond to some of your points; you will find similar advice among my older posts, but it never hurts to repeat the facts.

In the wild I don't think bettas would be the only fish in the stream/paddy. So they wouldn't be completely alone and unexposed to other fish their whole life which is why I thought rasboras would be a good, natural option.

I cannot definitely prove or disprove this thinking, but I do consider it highly unlikely that these fish would ever see each other in their habitats. The plakat betta is a form of Betta splendens, having short fins, but otherwise the same temperament/behaviours. Some sources suggest plakats may be a tad feistier (more aggressive in fighting) which is worth keeping in mind. Given the natural habitat of Betta splendens, I would think it highly unlikely it ever comes across small fish like rasbora. But this is surmise, admittedly, though logical given the natural habitats and physiology of the species.

I was suggested pencilfish because they are supposedly peaceful and prefer soft water like bettas do.

There is much more to community fish which has to be considered. Pencilfish are species in the single (at present) genus Nannostomus, and they are in the characidae family. Characins have teeth, often lots of them, and they do not hesitate to use them. Given the numerous distinct species in this genus there is considerable variation in inherent behaviours. The most commonly seen pencilfish, N. beckfordi, is a real terror with certain other fish; I have maintained and spawned this species for many years, but more than once I have had to move them from, or move other fish from, the aquarium, even when it was a 5-foot or 4-foot tank. They do not tolerate any other surface fish; my otos took a beating from this species solely because the otos dared to graze leaves near the surface. Another species, N. trifasciatus, had to be moved for much the same reason.

Then we come to the bright red species like N. mortenthaleri and N. rubrocaudatus. The intense red colouration of these two fish would almost certainly inflame most male bettas. Neon tetras are often targeted for the same reason. The males of N. unifasciatus can get nippy, depending. Other species vary.

That brings me to your comment,

I think whether or not bettas can be community fish is a matter of opinion and preference. In my opinion they can as long as the betta has the proper temperament and the community fish don't pester him.

It is risky to assume something that is contrary to the scientific evidence in the hopes it may work. Bettas are bred with heightened aggressiveness. Even if no physical contact occurs, other fish can read this chemically. In reverse, small shoaling fish that are normally peaceful can be provoked into nipping (or worse) when placed in the confines of an aquarium with fish that are sedate and have flowing fins. And here too, even if no physical interaction occurs, the Betta can read the signals. All fish release chemical signals called pheromones (read by the same species) and allomones (read by other species); this is a prime method of communication. We do substantial water changes to remove these (along with other stuff of course), because the chemicals are strong. They carry to fish in creeks, streams and rivers, so imagine their impact in the confines of (to the fish) a very small space from which it has no means of escape. And placed in that situation, fish either fight back aggressively, or they may withdraw and literally waste away.

We cannot change what is programmed into the species DNA, so it is wisest to learn those inherent traits and behaviours that can be expected from most fish in the species (the "norm" for a species) and respect them and provide accordingly. Your own experience with neons and the betta is what usually happens when we ignore them.

Feel free to question any of this.

Byron.
 
Last edited:
Some sources suggest plakats may be a tad feistier (more aggressive in fighting) which is worth keeping in mind

PK's are / were bred for fighting and are very aggressive.
 
The betta community fish debate is all well, I respect the points brought up here. But I still want to know why my rasboras are killing each other. I would witness the rasboras in the act of the bullying. Even when the first betta in the tank passed away and the tank didn't have a betta in it for a couple months, the bullying would still continue. I know my bettas have nothing to do with the aggression with the rasboras.
 

Most reactions

trending

Members online

No members online now.
Back
Top