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Fish aggression "ratings"- how valid/useful?

Trever

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I recently had a terrible experience with a fish that is notoriously considered peaceful (not even semi- aggressive). The fish was "bossy" during feeding but generally peaceful with tank inhabitants that were in place before the fish was stocked, though over time, less bossy (consistent with its peaceful reputation). But when a new addition was stocked (a different species also considered peaceful), the supposedly peaceful fish attacked the new addition and did so repeatedly, including grabbing the new addition by the head (more than once). This began the moment the new addition was placed "in" the tank in the temperature acclimation bag, where the peaceful fish charged the new addition, running itself into the bag where the new addition was lying in the bag.

Over the course of 2 days or so, it became clear the peaceful fish was extremely aggressive with the new addition, and that this behavior wasn't going to change; rather, one had to assume it was going to kill the new addition. (My LFS advised to remove the instigator from the tank.)

Either the peaceful fish was an unusually ill tempered specimen, or it had some distinct issue with the new fish that didn't seem to have anything to do with any factor you might name (territory, order of addition, size/maturity, coloration, etc.). Certainly it did not seem to have anything to do with any factor I could discern. The peaceful fish was just highly aggressive, at least with the new addition, and not with the other inhabitants.

I have read many postings, but I wanted to ask directly and see if anyone shares information that might be more clarifying.

How useful should we consider the aggression ratings commonly assigned to fish?

Part of the reason I ask is that I have wanted to stock a "semi aggressive" fish, because I like the fish. But I'm concerned about such a fish in my present tank. If these ratings aren't worth much, I'm inclined to add the fish (last fish to be stocked), in part since many relate good experiences with this fish, considering its reputation unjustified.

I am deliberately leaving out any mention of the species I have experience with or have in mind, because I'm interested in the more general question.

Thanks in advance.
 
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jgirardnrg

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It's coin flip... I just went through this. I have a 60g cube in my office and had 3 yellow tail damsels in there. One was the tank bully, the other two were beat almost to death. I moved them to the fuge in the sump to recover while I tried to catch the bully. He then started picking on the clowns and royal gramma. Long story short, I caught him and he's swimming in a tank at the LFS. Put the other 2 back in the tank and everything is peaceful... glancing over right now and they're schooling with the royal gramma at the moment... all swimming together peacefully.

You just never know with any fish. Some are just mean.
 

LiamPM

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I think the most important thing is to realise that all of these care level, temperament labels etc. are all just based from common experience. They should only be taken as a general rule of thumb. (I own a popular app, that lists these recommended labels for all species)

Every fish has its own personality and i imagine most of us that have been in the hobby for some time have had one at some point that acted out of the norm.

There are too many variables to answer the question without knowing though.

I think most would agree a 'Firefish' is a very peaceful fish but put 6 of them in a 6 gallon box they sure wont be. Thats a huge exaggeration but my point being that so many variables can effect aggression alone.

It's coin flip... I just went through this. I have a 60g cube in my office and had 3 yellow tail damsels in there.
To be fair though there is a reason most damsels get dubbed the 'devils' of the tanks their in. They acted pretty normal for you i think and id keep an eye on it happening again with the two left over time.
 

Tired

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How sure are you that you had a royal gramma and not a dottyback? Dottybacks are territorial enough that a whole 30gal can be their territory, and a wrasse is unfortunately shaped enough like them that it might get targeted as a rival. Royal grammas are generally considered peaceful to semi-aggressive because they usually only defend their exact cave, dottybacks are more towards aggressive.
 
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LiamPM

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@jgirardnrg so 2 out of 3 not in accordance with their reputation.
Id say they were in accordance to their reputation. Even LiveAquaria states " some may be territorial towards its own kind or similar-sized fish" ......You got one from the "some"
 

Tired

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As a general rule, fish are more likely to be aggressive towards similar-looking fish. Yellowtail blue damsels usually aren't too bad to other non-damsel fish, though they definitely defend a (small) territory, but in a small tank they really beat on other damsels. Watchman gobies couldn't care less about other fish, but get mad at other watchmen. It's because they're more likely to see a conspecific as competition. In the ocean, the competition would just leave if sufficiently bothered. Not so much in a box.

(And, just to nitpick: there aren't really any saltwater fish easily available for aquaria that school. Some shoal, but usually with their own kind. Multiple fish of different species hanging out in the same general area isn't really schooling or shoaling, that's just them getting along. It's cute, though.)
 

saltyhog

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Any fish that's questionable I would ask the fish guys here before adding. For instance, almost all wrasses are listed by most merchants as "peaceful"....and they are to dissimilar fish. However, certain wrasses are almost always intolerant of other wrasses in the tank (Scott's fairy, 6 line come to mind). I would always do research beyond just the vendor's recommendation with any fish.

As noted above, you also have to make allowances for fish that have individual variations from the norm. My alpha fairy wrasse is an Exquisite and they are not known to be aggressive with other fairy wrasses very much.
 

j.falk

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Were the 2 fish the same colors? I've noticed that similar colored fish will tend to fight with each other...even those that are deemed "peaceful". But then again fish are like people...no two fish are the same. We get along with some people...others we don't like for whatever reason.
 
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Trever

Trever

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@saltyhog the fish I'm interested in seems to fall into a grey category... it's a damsel, but the Azure. That would be a "tell me about Azure Damsel" post, though. Just interested here more in understanding what guides us in understanding fish behavior, as it were. It does seem pretty uncontroversial that SAME species together, as you say, is a guarantee of aggression (unless done right, where that is possible).
 
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Karen00

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So far I have found most ratings to be true but have noticed a remarkable change in my peaceful fish either when I had too many for the space or when they became of breeding age (mainly the males becoming very territorial) so then the size of the tank for the number of males also becomes an issue. Typically their aggression was only toward their own species but once they spawned then everyone became fair game if the intruders came too close to the nest. I think in some cases, depending on the fish, it would be best to have a species specific tank as to not inflict unwanted stress on other species in the tank that can become targets. Afterall their ability to get away is limited in a tank compared to the ocean (or lake, stream, river, etc for fw). Species only tanks goes both ways... Either the fish is too aggressive against other tank mates or is too docile (like seahorses.... Especially the dwarfs or so I have rwad) and each type would benefit having a tank of their own).

I think like any other creature on the planet they can be fine until some event takes place in the tank that sets one of them off (could be a new fish or the balance in the tank has been disrupted, have come into breeding age, etc). It is a toss of the coin as others have mentioned because you never know what that event might be. That's when a plan B is needed if this happens (setup a new tank for the troublemaker(s) or rehome or bring to LFS).
 
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Trever

Trever

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@j.falk I said it didn't seem to depend on color but that is main thing I have wondered about. Thing is, my peaceful fish would then be known to not do well with fish that have some of it's coloration... whereas what I had is regarded as among the quintessentially peaceful fish.
 

Tired

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Again: how sure are you of the species? Royal grammas and royal dottybacks look very similar, but one is less peaceful. The easiest way to tell the difference is to check the dorsal fin for a black dot. Grammas have it, dottybacks (ironically) don't.

Also, royal grammas are not 100% peaceful anyway. And they're a relatively slender-bodied fish, with some yellow on them. A yellow coris wrasse is a similar body shape, with lots of yellow on it. Possibly close enough to be seen as a threat.
 
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Trever

Trever

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@Karen00 I can't imagine buying my fish from an LFS that accepts returns, but that's another story. (My LFS follows strict quarantine protocols, which is why I pay a bit more and drive a good deal further to use that LFS.). I have to talk to her today though, because she may have given me a fish that got put back- either from her own tanks in some way (eg. taken out of store DT) or someone who perhaps she knows she can trust (her husband!). I said I didn't want that fish, but anyways, more evidence that what I had was a trouble maker if I got something that had already caused trouble elsewhere. But that just reinforces that ratings are less than useful, if an individual can be so contrary to its reputation. (Would also mean I have a bone to pick with my LFS for giving me a bad fish!)

My tank is somewhere between appropriately and lightly stocked, is what my research says. When it had 4 fish, that seemed about perfect to me, though I can imagine many people would add more, I felt satisfied. Also, the fish have different areas they prefer (sand vs. rock vs. the silly clowns who seem to like flow and randomly exploring- we'll see what happens once coral are present), and from what I've seen so far, where fish hang out on a reef must make a huge difference. Seems like this would be right up there with avoiding same species in one lower volume tank. It seems like a huge factor to consider, based on watching how my fish coexist in the tank.

Something like a bichromis dottyback is often regarded (from what I've seen) as a species specific tank kind of fish. So yes, but from the stories I've heard, fish like that (or something dainty) need their own tanks usually. I avoided that fish because of this. (Too bad, beautiful fish!)

But for eg. a lot of people seem to put an Azure Damsel in mid size and above tanks, without issues. Others hate anything with the word "damsel" in it.

I got the impression prior to my recent experience that what I had could basically never act as aggressively as it did, as long as it wasn't another fish of the same species. Clearly, that is not the case. So there is at least that point, with respect to ratings.
 

shred5

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Most peaceful fish are peaceful most of the time and most aggressive fish are aggressive most of the time. There can be a exception. You put a aggressive fish with a more aggressive fish and the first one can become peaceful.

Sometime fish are mislabeled or has another species that looks pretty close.

The thing is most saltwater fish can be territorial and the smaller the tank or less hiding spaces or dens can cause a fish to defend its territory. Now take that same fish and put them in a tank with more room or lots of caves and that can go away.
Take a Royal Gramma and put them in a tank with one den. That royal Gramma will defend that one den.

New additions can always be tough. Allot of fish have territory staked and new fish are rarely welcomed in the saltwater world especially in a small tank. I have a Azure damsel which is a peaceful damsel but when I add a new fish he no longer is. The aggression goes away after a day so I always have to add more than one fish when I do so that aggression is spread out some.

Pairs can become aggressive especially when it is breeding time. Clowns are good example. Some of the most peaceful ones has eggs and they will go after anything. Sometime when they find that place to lay eggs.

By knowing some of the rules sometimes you can keep fish together most can not.

For example I do keep Royal grammas together and they get along fine. Would not work in a small tank. Funny thing is they hang out together and only bicker occasionally over only what I can imagine is the better den. I could at this point not add another because those existing would most certainly gang up on the other RG.
 

Karen00

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@Karen00 I can't imagine buying my fish from an LFS that accepts returns, but that's another story. (My LFS follows strict quarantine protocols, which is why I pay a bit more and drive a good deal further to use that LFS.). I have to talk to her today though, because she may have given me a fish that got put back- either from her own tanks in some way (eg. taken out of store DT) or someone who perhaps she knows she can trust (her husband!). I said I didn't want that fish, but anyways, more evidence that what I had was a trouble maker if I got something that had already caused trouble elsewhere. But that just reinforces that ratings are less than useful, if an individual can be so contrary to its reputation. (Would also mean I have a bone to pick with my LFS for giving me a bad fish!)

My tank is somewhere between appropriately and lightly stocked, is what my research says. When it had 4 fish, that seemed about perfect to me, though I can imagine many people would add more, I felt satisfied. Also, the fish have different areas they prefer (sand vs. rock vs. the silly clowns who seem to like flow and randomly exploring- we'll see what happens once coral are present), and from what I've seen so far, where fish hang out on a reef must make a huge difference. Seems like this would be right up there with avoiding same species in one lower volume tank. It seems like a huge factor to consider, based on watching how my fish coexist in the tank.

Something like a bichromis dottyback is often regarded (from what I've seen) as a species specific tank kind of fish. So yes, but from the stories I've heard, fish like that (or something dainty) need their own tanks usually. I avoided that fish because of this. (Too bad, beautiful fish!)

But for eg. a lot of people seem to put an Azure Damsel in mid size and above tanks, without issues. Others hate anything with the word "damsel" in it.

I got the impression prior to my recent experience that what I had could basically never act as aggressively as it did, as long as it wasn't another fish of the same species. Clearly, that is not the case. So there is at least that point, with respect to ratings.
I think that is exactly the point.... You can never have a 100% guarantee on a fish's personality. Maybe your fish had a personality disorder (I mean genetically there was something wrong with it) or maybe it was beat up in another home and turned aggressive (like a once peaceful dog being beaten and now it's not so peaceful). There are a ton of reasons why a supposedly peaceful fish can turn into demon or come to you as a demon. That's why everyone says to have a plan B. I also didn't say all fish stores take fish back. I was simply listing some plan B options. Most of the stores in my area do take them back. They have signs up saying as much. One of them even takes fish they didn't sell you.

I don't know why anyone would think fish are expected to act any different than other creatures on the planet. Any and all creatures can have personality shifts. Obviously the ratings given to fish come from how they typically behave in the wild (and co-exist with others or don't co-exist with others) and typically how they behave in tanks but there is never a guarantee in life for anything. Plan B, plan B.

My experience with all of my fish has pretty much been spot on so far but tomorrow (and my next fish) could be a different story. You asked how valuable the ratings are. I would say so far they have been accurate but that doesn't mean to say I haven't had my troubles for the reasons I mentioned.
 

saltyhog

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I had a single Azure in a 6 foot tank with no problems. Problems with them go up as tank size decreases and the number of Azures increases.

I think the guidelines are just that...only guidelines. I would only use them as a starting point and get further input if there is any doubt about the feasibility of a particular fish.
 

jgirardnrg

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Id say they were in accordance to their reputation. Even LiveAquaria states " some may be territorial towards its own kind or similar-sized fish" ......You got one from the "some"
I definitely got one from "some"... he was a terror to EVERY other tank inhabitant. Hermits, snails, other fish. He was also, by far, the most skittish fish in tank ironically. The other fish come to the front of the tank when I approach. He'd dive in the rocks and hide. Took a lot of patience and modifying a fish trap to finally catch him.
 
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