Denisoni Barbs + Rainbow shark

[swozzie]

I have had a Rainbow shark for around 3 years, most of that time he has been on his own but with a few small fish in a 4ft tank. I have just moved him to a well planted 180 litre tank. He is about 5 inches big. He seems to have established the lower part of this new tank as his territory.

2 days ago I added 4 Denisoni Barbs to the tank and the Rainbow shark is doing nothing but constantly chasing them (usually he just sits in his corner all day while the lights are on). They don't seem too worried about it though, they just duck out the way and then carry on eating or doing whatever they were doing before he interrupted them. I haven't seen him actually hit one of Denisoni's and if they don't swim away, the Rainbow shark doesn't do anything but the moment they do swim away he is after them. Each chase only lasts a second or two.

When the tank lights are on and its dark in the room the Rainbow shark can see his own reflection in the tank more vivedly and once that happens he doesn't bother the Denison's at all but spends all his time fighting/displaying against his own reflection.

For about an hour yesterday they were all swimming about together quite happily with very little chasing which was very surprising, but then I put an algae tablet in the tank and he got a bit possesive.

My question is, is this a phase the Rainbow shark is going through until he gets used to other tank mates. Is he being aggressive or just playing? Maybe he is boisterous because he has other tank mates? Maybe he is terratorial and wants to kill the Denisons! Like I said, the Denisons don't seem scared or bothered by him, they are much nippier fish and seem to be able to avoid him easily.

 

[Pointy_kitty]

i would say he is bothered by the new tank mates and will get over them in time, but rainbow sharks are notorious chasers
its like you described
he's alright until you feed them, then he gets into a frenzy and goes after them
this is pretty much unavoidable behavior
that is unless you stick him in an even bigger tank
but he would still have his reflection foe ,
so i would have to say that is unnessisary unless someone stops eating or is really showing stress
but the fish you described are tough little scrappers
so they shouldn't be bothered
just quick on their toes (hahaha or fins )

 

[Lateral Line]

Many of the "Sharks", Labeos mostly, hate their own kind, other shark species and pretty much anything that looks remotely like another shark. He may well just be flexing his muscles to make sure the new fish know who is in charge, but denisonii stress quite easily, so I'd watch them carefully for a while.