Discus chasing

[Oli]

I have a group of 7 discus in a 350 litre tank. All probably 5 inches and brought at the same time. Recently, the smallest one (only by a little bit) is being relentlessly chased and nipped at by every other discus. I understand sometimes having one bully in the tank, but it seems odd that the other 6 are all ganging up on this one, could there be something wrong with it?

 

[FranciscoB]

Not knowing other details -and even knowing- it sounds as if that fish is at the bottom of the pecking order. It will be harassed relentlessly and outcompeted for food. It is tough with discus behavior. Sometimes, adding more decorations and complexity to the tank will make a big difference, but not always.

 

[Colin_T]

Need a video showing the behaviour. Upload videos to YouTube, then copy & paste the link here. If you use a mobile phone to film the fish, hold the phone horizontally (landscape mode) so the footage fills the entire screen and doesn't have black bars on either end.

We also need a picture showing the entire tank so we can see how it's laid out.

The fish are probably sexually mature and setting up territories and the smallest one could be a male that is being bullied by other bigger males. Separating the fish is the only permanent solution if this is the case.

 

[FranciscoB]

Separating the fish will indeed sometimes work. Except that the single discus is unlikely to thrive on its own either. Also, quite often, the next lowest in the pecking order will become the target, repeating the issue on another fish. There will almost always be a hierarchy. Physical structures around the tank, such as pieces of driftwood help immensity in allowing respite for lower ranking fish. Also, contrary to what commonly assumed, large females can be relentless on low ranking fish.

 

[Fishfunn]

I wonder, if you separate the smaller discus from the others, does their aggressive behavior still happen?
You might have to exchange that discus at the LFS for one bigger? Discus are cichlids and they are aggressive by nature. In the past, the only way I had discus are by a mating pair or single otherwise they fight all the time.

 

[simonas]

You'll need to address that probably by removing it and maybe adding another as suggested otherwise it'll shy away and not eat and fade away. Discus are a pain for it, think I have about 13 in my tank now and its odd how the pecking order can change also