introducing new small fish with aggressive dominant...

[Sk8r]

1) it helps if the species are not predator/prey or incurably antagonistic: research.
2.) get new small fish (NSF) in net, carry them down and release low into many-holed rockwork.
3) feeding may not be a good move. You don't want the aggressive dominant (AD) to mistake the NSF for lunch. Feed the AD an hour earlier, and give him plenty.
4) take every net you own and set them net-end down on the sand, handle resting upright on the rockwork; if you don't have that many nets, just use weird safe foreign objects like tubes and pieces of eggcrate and such. And be prepared to leave them that way. This will inhibit and intimidate the AD and the NSF alike, but the AD probably more so. Put one of the nets so as to close off easy access for the AD to the hiding place.
5) cross your fingers and just do not try to intervene at this point. There is nothing much you CAN do. If the NSF have decent instincts, they'll lie low in the rocks, and keep out of open water. Be careful feeding: you do not want to feed immediately: give it overnight; and you do not want to lure the little guys out when you do: feed stuff like flake that will spread fast and be generally available in sizes for all mouths. I put Selcon into the water at feeding time in the theory that it will boost appetites and get into the systems of the stressed fish, helping anybody who got a nipped fin.
6) hope that a couple of sunrises will dim the memory of new additions and make the AD think the NSF have always been there.
7) gradually, over several days, withdraw your scarecrow objects, the one protecting the nest last of all.
With luck, the AD will think of the NSF as part of the scenery now.

7)

 

[BigEZ77]

Interesting. What about putting the AD in an acclimation box in the tank while the new fish settles in? I have a Bubble Magus trap that doubles as a quarantine box that I was thinking of using if I ever find myself in that situation. Like the multiple items that intimidate the AD to take its attention off the new fish though.

 

[Sk8r]

That can work. So can an eggcrate divider if you can make it fit and stay---a corner is sometimes a bet. YOu can also remove AD to quarantine until he's the New FIsh.

 

[Maritimer]

Great write-up as always, Sk8r!

What about setting a mirror alongside the tank, so the AD is distracted by the conspecific "interloper"?

Would adding multiple newbies at the same time help? (I know it won't help the biofilter, but...)

Also, wondering if it might help to set the powerheads in a pulse/surge mode that would simulate an ocean storm temporarily? Would the change in flow act as a distraction?

_Love_ the advice about leaving a few nets, etc... in the tank!

~Bruce, who's currently facing just such a prospect . . .

 

[Sk8r]

The nets are a pretty good intimidation: we all know how fish go for the rocks when nets are deployed. Multiple fish can distract, or all become lunch. A mirror at the other end of the tank, maybe, but depending on the species. A hot-tempered individual may begin to lash out at everything, but you can use that with some species---I've known a placid yellow watchman nearly blow a gasket at the sight of a mirror. It's very much a play-by-ear and use your species knowledge. Having prior knowledge of how certain species do get along (when things are working) does help. But getting the little fish down low into shelter is a really good thing IF they will just have the sense to stay there and not get spooked out.

 

[Reef Frog]

I am getting ready to release 3 small fish into the display tank at the same time with an AD Royal Gramma that can be a "soft bully" to a few select fish. She flares her gills and keeps certain fish behind the rock work but doesn't bite.

I'm hoping to upset the current social order a bit, giving the shy fish the opportunity to spread their wings (fins ?) and giving the NSF a chance to get comfortable with minimal aggression from ADRG. In theory this could diffuse aggression but only time will tell. I've ever only introduced fish one at a time in the past.

I like the idea of putting a bunch of new objects in the tank temporarily. I don't feel like rearranging the rockscape which is sometimes suggested.

 

[Sk8r]

It's like a rock rearrangement, but perhaps even more intimidating.

 

[Tisbe]

What has worked well for me is. Move the rocks around and/or add things like pvc pipe pieces in the evening when the new guys is going into the tank. Basically make the old fish think they are in a new home. Then add the new guy when the lights are out and the old tank mates have gone to rest for the evening. These two things seems to temporarily reduce some of the aggression in the tank while the old fish start to get used to their new environment.

 

[hkgar]

Anyone suggesting removing the AD tried to catch a fish in an established tank. Trapping is the usual method but no guarantee the right fish will get trapped

 

[Sk8r]

And sometimes with a reef you can't move rocks. It's well to have a full repertoire of methods.

 

[Hal]

Interesting. What about putting the AD in an acclimation box in the tank while the new fish settles in? I have a Bubble Magus trap that doubles as a quarantine box that I was thinking of using if I ever find myself in that situation. Like the multiple items that intimidate the AD to take its attention off the new fish though.

This has worked for me numerous times. I use a reptile critter keeper (large size I think), available at most pet stores or online, with extra holes drilled in the sides for water exchange/flow. Add a few pieces of pvc and/or plastic plants for hiding places, and voila!

Leave the NSF in the acclimation box for about 3 days. Upon release you should see minimal to no aggression from the existing fish.

 

[marleesan]

Would my cherub angel count as an aggressive dominant in my 37 gallon? I am looking to add one more fish after him so I might need these tips soon

 

[Sk8r]

He may well. Be prepared. But I'd watch that valentini puffer around angel's tail...

 

[BrianKC]

What has worked well for me is. Move the rocks around and/or add things like pvc pipe pieces in the evening when the new guys is going into the tank. Basically make the old fish think they are in a new home. Then add the new guy when the lights are out and the old tank mates have gone to rest for the evening. These two things seems to temporarily reduce some of the aggression in the tank while the old fish start to get used to their new environment.

I used to do the lights out thing, but my last addition accidentally stumbled into my tang's resting spot, got chased out of there, straight into the pistol shrimp's cave and got his fin snapped. It all worked out, but I think adding the fish in the dark is a challenge for the new guys because they can't see where might be safe to go.


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