Black Shark started acting nuts

[Nick Park]

I have a 14" Black Shark (Labeo chrysophekadion) who, for the last 8 months, has been boringly predictable in its behaviour. It hides all day in a cave at the back of the tank, then comes out at night once the lights are out, disappearing back into the cave as soon as anyone enters the room. The cichlids in the tank keep out of its way, and it rarely bothers them.

Today, while the cichlids were being fed, it seemed to go nuts. I heard a huge thump from it hitting the back wall of the tank, then it emerged into the open with scales flaking off one side (where it appears to have just scraped itself against rocks at high speed).

Now it's hanging out much more in the open (something it never does when the lights are on) and my 3 heros efasciatus, which normally stay well out of the shark's way, are acting much more aggressively towards it, warning it off from their corner of the tank.

The wounds to the shark's body appear superficial, with the greatest damage around its left eye - but thankfully the eyeball itself appears unharmed.

Anyone with experience of keeping these fish got any idea what might be going on here?

 

[tlindsey]

I have a 14" Black Shark (Labeo chrysophekadion) who, for the last 8 months, has been boringly predictable in its behaviour. It hides all day in a cave at the back of the tank, then comes out at night once the lights are out, disappearing back into the cave as soon as anyone enters the room. The cichlids in the tank keep out of its way, and it rarely bothers them.

Today, while the cichlids were being fed, it seemed to go nuts. I heard a huge thump from it hitting the back wall of the tank, then it emerged into the open with scales flaking off one side (where it appears to have just scraped itself against rocks at high speed).

Now it's hanging out much more in the open (something it never does when the lights are on) and my 3 heros efasciatus, which normally stay well out of the shark's way, are acting much more aggressively towards it, warning it off from their corner of the tank.

The wounds to the shark's body appear superficial, with the greatest damage around its left eye - but thankfully the eyeball itself appears unharmed.

Anyone with experience of keeping these fish got any idea what might be going on here?

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I know that Adult Black Sharks are known to become aggressive but in your case I would remove the Black Shark before it gets killed.

 

[thebiggerthebetter]

It sounds like you have a community of aggressive fish and it may be hard to say what's going on because the interaction of aggressive species can vary greatly from tank to tank. Still, in many cases there could be rules and exceptions observed. Since I don't know anything about your Heros cichlids or what else is in there with them in your tank, I hope you provide a more complete list and someone apt with cichlids will help you.

My black shark is about 10" and is housed with several catfish species, VATF, pbass, and African arowana. If it could, it would probably hide all day, as yours does, so here our observations match. It gives an occasional chase to some tank mates but nothing serious.

Before, mine was housed with a purple Labeo, Prochilodus lineatus, Distichodus lussoso, dorado, and banded leporinus. I had to move it to a different tank as it started losing the batte with its very aggressive tank mates.

 

[moe214]

Sounds like a change in hierarchy to me. All the fish I've ever kept were territorial. Reminds me of when I got a small buttikoferi, and it grew quickly to 10" and slowly made its way up the hierarchy. Got rid of it before it made its way to top dog, didn't want it and the jag fighting and didn't know how aggro it'd be as top dog, knowing my jag was a safe bett being more of a peacekeeper.

 

[Nick Park]

I purchased the tank second-hand with the fish already in it, so the mix is not something I would have chosen myself.

It's a 450 litre tank, and apart from the Black Shark it contains the following:
3 heros efaciatus (between 5-7")
a 6.5"synodontis catfish
a 5" blood parrot
a 3.5" jewel cichlid
13 assorted mbuna

There's been no inter-species aggression. The only serious aggression has been a homicidal jewel fish killing 2 other jewels, and male mbuna fighting among themselves over females.

The Black Shark's sheer size intimidates the other fish. It occasionally chases them away from its food at night, but nothing serious and they back away pretty sharpish. Its present injuries do appear to be self-inflicted.

The tank is well filtered (an FX6 and an Eheim 2229). Ammonia and Nitrites are zero, pH is 8.2, and nitrates 40 ppm. I do 35% water changes twice a week.

 

[Nick Park]

I know that Adult Black Sharks are known to become aggressive but in your case I would remove the Black Shark before it gets killed.

I've nowhere to put it!