World War 3 In Tank

[caggimedicine]

I recently decided to change a few things around in my tank and have removed a lot of stuff - I had various rocks, slate, loads and loads of plants... and have simplified it all now. There's just one very large piece of wood in there and a few plants.

It's a 50 gallon established tank. I've got 2 silver dollars, 2 large bala sharks, 1 angelfish, 1 pleco - had all for about a year or two.

Although my stocking seems a little strange, all was well and peaceful in tankworld... until this week when all hell broke loose!

The largest of my 2 bala sharks is chasing everything around the tank - he's angry with the world it seems.
One of the silver dollars is having a go at the other one - albeit occasionally
Even my usually peaceful plec is now making regular trips out from underneath the wood and actually lunging at the fish in a bid to have a go!

The only happy one seems to be my angelfish who is swimming around as if nothing's going on.

Obvious possible causes:

1. Shouldn't be just 2 sharks and silverdollars - I know... I'm planning on getting at least another one of each
2. The change around of the tank may have disrupted territories

Do you think it's just one of the 2 obvious things above, or could it be something else?

 

[minnnt]

Possibly number two mate. If they have a 'new' tank maybe they are just asserting themselves. Also if there is not enough 'dividers' in the tank such as the rocks etc which can act as territory boundaries then the more dominant of the two will think the whole tank is theirs.

Maybe, not really sure though.

 

[Duz]

Well the 2 obvious reasons you have stated.
1. When the fish are mature they may become a bit more aggressive (this normally happens when they get older so they can fight for their territory).
2. Because you have changed the tank layout, the fish now need to restablish their territory. If you look at it from a fish point of view, they have territories so when a future mate comes along they can have them all to themselves so long as they are in their territory. They don't actually know they are in a glass box. However, if they are just sorting out their territories again they should settle down within a week or so, they may occassionally have a little go at each other but it shouldn't be as strong so to speak.

If the problem continues after a couple of weeks, try to break up the lines of sight within the tank with plants/decor as this will reduce aggression levels. Clear lines of sight mean that the fish have a chance to see each other and consequently this will lead to aggression. The plants/decor act as a clear boarder which is why they can help to reduce aggression levels. Hope this can help!

 

[caggimedicine]

Thanks everyone - i'll keep an eye on how things go over the next week / two and see if they calm down a bit. The main 'culprit' appears to be the large bala shark - I think he's the trouble-maker.