Incompatible tank mates or bullies.

When introducing a new tank mate, how long should it take for everyone to settle in? Is there a time frame for dominance to be established between different species? If you add something new to a tank and an existing fish relentlessly attacks it, is it safe to say they aren't going to work it out?

That's probably a safe bet, what type of fish are we talking about?

Steve

A certain amount of sparring for an hour or so is normal. After that, you have a fish with a territory and a fish it sees as a threat. In the wild, the threat swims off if it loses. In the tank, it is trapped, but the holder of the territory is too - it is challenged by the presence of the intruder that by staying, signals a fight to the death for the turf.

Just a couple of examples,

I picked up a saltwater tank last spring that had among other fish a pair clownfish in it. So I introduced all the fish to my existing tank and everything went fine.Except between the female clownfish that was already in the tank and the male just moving in. They chased each other around for about a half hour until I decided to pull them out. Ever try to catch a pair of fish that were freaking out in a tank full of live rock? Let’s just say I had rearranged the whole tank. I ultimately decided to remove both pairs for a few days and reintroduce them at the same time. The hope was that neither pair would have setup shop and they might actually get along.

It seemed that it had worked and I watched them closely for a couple of hours before heading off to bed. The next morning was a different story, the new pair was in rough shape. I removed them but they succumbed to their injuries a few hours later.

Also last spring a picked up a Koi that was about 18" long,

I introduced him to a 350 gal tank that had about another 50 other koi and goldfish in it. One of the existing fish was about the same size as the new fish. The one that was in there to start with went at the new one like a crazed dog. This 5+lb fish was attacking another of the same size when he was surrounded by a bunch of others. Made no sense to me, but I ended up removing him after about 15 minutes.

I have found that I end up with the most issues between fish of similar types

Steve

My daughters betta, can't be with anything else, ever. We've tried it with a few different things but he's just mean.
I was asking because my daughter got an aquatic frog yesterday. We were assured it would be fine in the 10 gallon tank with the 4 neon tetras and one bushy nose pleco. The second we put it in the tank the pleco went after it and never stopped. I watched for about 20 minutes before intervening and shooing them to opposite sides of the tank. The pleco seemed to ignore the frog so we went for supper but when we came home it was the same thing, pleco chasing frog everywhere relentlessly. He even tried to suction himself to the frog! I ended up taking him out and putting him in the 33 gallon with the other pleco and the snails. He pulled the same crap but that pleco is bigger and pushed back so now they seem to be fine. Obviously though I need another bottom feeder for the 10 gallon. There were some little albino cory's that my daughter fell in love with, think they'd work?

Sometimes there is just no rime or reason to it, you get a fish that just doesn't play nice. If you do get fish with bad reputations, it helps if you can get them young and have them grow up together. I picked up a clown tang last spring when he was the size of a quarter. he gets along great with the rest of the tank, even though he is now big enough to eat the rest of them.

Steve


Steve

The frog's seen as a threat to the pleco.
Which is okay, as Mr Frog will probably try to eat the neons. It can't eat Corys due to their defensive spines though. Aquatic frogs prove the 'if it will fit in the mouth, it will be tried". The neons may be too fast.
The tank, as a 10 gallon, is really small for an Ancistrus - much too small. That's probably part of the problem. It's only good for maybe 6 small fish.

My Tiger and Green barbs are like that as well. They are constantly harassing each other singling out the weakest with nose-to-nose combat, and then they all gang up nipping fins and chasing the individual all over the tank.

Size does not matter with these guys either.  In January, I added a very small Tiger about a half an inch long to a tank with adults and he immediately started taking over the tank. The little guy was so quick the older guys couldn’t get out of the way fast enough.
On spawning days, all hell breaks loose with a male and female trying to find a dense plant to deposit their eggs, after spawning all the other barbs dive into the plant eating up all they can before being chased out by dad

Other days everything is calm and quiet, so who knows what goes on in those little fish brains  
A very interesting species that is for sure

What about moving the decorations around before introducing new fish? I was told that this can help the fish to reestablish their territory. We did not do this when we introduced our Dennison barbs, and a person from a local fish shop said that this may have helped. I have never actually done this, so thoughts or experiences?

Shell wrote:What about moving the decorations around before introducing new fish? I was told that this can help the fish to reestablish their territory. We did not do this when we introduced our Dennison barbs, and a person from a local fish shop said that this may have helped. I have never actually done this, so thoughts or experiences?

I can lend some evidence to that. Any time I move decorations or plants around in the tank, my ram going crazy "re-establishing" his territory. It'll go on for a half or hour, and then he calms down.

I went back to the pet store last night and had a chat with the guy working the fish area. He said there's no way my pleco was attacking the frog, it's never happened, blah blah blah. Then I showed him the pictures I took and he decided maybe it's possible after all.
The 2 pleco are doing fine in the bigger tank. They'll shove each other around a couple times then retire to either side of the tank and go on their merry ways.
I ended up bringing home a really tiny albino bristlenose for the 10 gallon. Supposedly it won't get much bigger, will take care of the algae in that tank and is compatible with the rest of the tank inhabitants.
The guy at the store said because it's smaller than the frog and blind there's virtually no way there will be a problem. So far that seems to be true, I guess we'll wait and see.
As for the frog and the neons, I haven't seen any sign of the frog going after them. The pet store people assured me the frog would be fine with anything.
I did hear the guy at the pet store last night tell a guy buying cichlids to rearrange his ornaments before adding the new one or it would be attacked so maybe there is something to that idea.

There's a lot to rearrangement as an idea - it's a tried and true trick. If you keep malawi cichlids, it's a necessity every time you add a new fish, or else.
It depends on how a fish sees territory though.
A Cichlid, a pupfish, an anabantoid or some of the osddballs orient themselves by landmarks. So moving a landmark disorients them enough that they have to rearrange their whole world in their minds. They do that quickly (nature changes rapidly) but since moving stuff destroys their sense of their own space, they'll let some other fish in during the period of confusion, and the other fish can often grab a bit of territory for itself.
Barbs, rainbows and other open water fish orient power by rank. An alpha tiger barb knows who's boss in the group, and has to show that to a newcomer. Those fights are usually short and direct. The alpha drives the weaker fish into its place in the hierarchy, and life goes on.
The territory holding fish have more to lose than status, so they are rougher with newcomers if there are no decor changes. That territory is their shot at mating and raising young. Most 'placeholding' territorial fish somehow care for their young, and no place equals no young. They can be ferocious with intruders who threaten what they see as good broodcare territory.
Odd are your bristlenose is male. Ancistrus spawn in caves. The male waits for females to come to him, and he guards the eggs and the young with his life until they can swim on their own. Your guy wants to breed, and if the frog takes his place, he never will (in his instincts). Mr Bristlenose had a lot at stake in that squabble. I doubt the frog was any danger to him, but that's how he read it.
Dwarf frogs will take surprisingly large fish. I've seen pictures of them with neon sized prey stuck in their mouths - they will certainly bite off a lot more than they can chew.

Thank you for all that info GaryE. There is so much to learn and I am fortunate to have come to a place where that information is so freely shared!