How many Chromis do I need/should have?

[Haleyf1024]

I have set up my 110 gallon and am finally ready for the first fish. I will be getting blue/green chromis, about 1/2-1" long. The tank will later have a tang, some clowns, a valentini puffer, and a few other smaller fish. I have heard answers from 3 all the way up to 10. I know they can get aggressive and kill each other so I don't really need that rehashed. Thanks in advance

[Betta132]

One. Any larger number will lead to deaths. Plus, they often come in sick.
If you want a chromis school, there are other types that aren't as mean as the blue-greens. Or, perhaps threadfin cardinals instead? Those are peaceful towards each other.

[snorvich]

Originally Posted by Betta132

One. Any larger number will lead to deaths. Plus, they often come in sick.
If you want a chromis school, there are other types that aren't as mean as the blue-greens. Or, perhaps threadfin cardinals instead? Those are peaceful towards each other.

this. Be very careful as they are highly susceptible to uronema marinum which is one of the worst parasites.

[SoloChromis]

The more chromis you have the more the aggression will be evenly dispersed, however you're going to probably need around 10 I'd say, which takes quite the toll on your biological filtration. I know you said you don't want to hear of their conspecific aggression again, but whatever you heard was some valid advice. I have personally never seen a situation where a group of blue/green chromis lasts more than about a year or 2. Where I used to work we had a 3,500 gallon reef pond/coral retail tank, and we could never manage to keep more than maybe 5-6 in this gigantic tank, no matter the space available and how often we fed the whole tank. It's a strange phenomenon, but the condition these fish come in nowadays is awful and the one's that *do* survive tend to pick each other off anyways until theres only 1-2. Beautiful fish, with the shimmery turquoise coloration though, so if you like them, I'd go ahead and get 1-2, but adding a group probably isn't in your's, or the fish's best interest. Good luck

[Betta132]

Even groups of 10 can be gradually whittled down to one or two. It's really not worth it... too many fish die slow deaths every time someone tries to keep a school of them.

[Haleyf1024]

I really want a school of them I have seen pictures and read other's comments on old posts that had schools for 4+ years with no aggression. Are all of you saying this out of first hand experience? Darn They are being kept with a huge 8"+ Sohal tang in the LFS and there are probably 50+ of them in there with other damsels. There doesn't seem to be any aggression in the tank, they actually cower away from the tang together in groups of like 10 under a rock to watch him swim by lol.

[Dmorty217]

Zero... don't get one

[Betta132]

They're terrified of the tang, which keeps them too scared to fight. Also, they're probably young. Put them in a non-stressful place, and you will most likely have fighting. It is possible to have a school of green chromis, yes, but most of the time there are deaths.
Now, there are species of chromis other than blue-greens, and some of those school just fine. I suggest looking into those instead.

[dogface 13]

I have a 180 gallon and I have 6 chromis, they have grown together and seem ok. They are large now, and are cool to see school together and move around.

[daquan44]

I started out with 10 blue green chromis in my 125 g and two years later I have 6. I have not observed any aggression. The first two died early on because they were small and sickly. I have no clue what happened to the other two. The rest are fine. They don't school like they use to. They each do their own thing, mainly swimming in between my sps corals. I think it is cool how they sleep at night. I cannot find them at all when the lights go out.

[SoloChromis]

Originally Posted by Betta132

They're terrified of the tang, which keeps them too scared to fight. Also, they're probably young. Put them in a non-stressful place, and you will most likely have fighting. It is possible to have a school of green chromis, yes, but most of the time there are deaths.
Now, there are species of chromis other than blue-greens, and some of those school just fine. I suggest looking into those instead.

Supposedly the Vanderbilts are pretty sociable with each other, and lately I've been hearing good things about the black axils (how convenient that they also cost much more than the other species ). Whether or not there is any basis to these claims is arguable, but I do believe certain species are more relentlessly aggressive with one another than others, for example blue reef chromis (Chromis cyaneus) and black & white chromis (Chromis margaritifer) are especially mean to each other IME. In fact I have to yet to see either of those species being kept in a group of more than 2 (if you can call that a "group"), in which case they either tolerate one another due to a large expanse of territory or they are to some effect a pair. I'm always a bit skeptical when I see how often the more expensive fish are magically granted "desirable" traits, that others of their genus or family somehow conveniently lack (according to retailers). Not necessarily that they are hardier, but that they are more peaceful, become more attractive etc. etc.

[SoloChromis]

Originally Posted by Haleyf1024

I really want a school of them I have seen pictures and read other's comments on old posts that had schools for 4+ years with no aggression. Are all of you saying this out of first hand experience? Darn They are being kept with a huge 8"+ Sohal tang in the LFS and there are probably 50+ of them in there with other damsels. There doesn't seem to be any aggression in the tank, they actually cower away from the tang together in groups of like 10 under a rock to watch him swim by lol.

The monster sohal tang may be scaring them into submission. This is often the case, where schooling fish need some kind of perceived threat to keep them in line, seeing as they feel they need one another to survive. Granted the sohal is not a true predator, but their violent tendencies often stress tankmates out, and I'm assuming the same applies to the chromis you're talking about. What size are they? Often juveniles will coexist pretty well until they start reaching maturity and see each other more as competition for resources

[Deinonych]

Originally Posted by Dmorty217

Zero... don't get one

+1, see Snorvich's post above. If you must have one, quarantine it, and only quarantine it by itself. They are highly susceptible to Uronema infections (especially this time of year for some reason), and you don't want that in your DT, trust me.

Chromis don't school in captivity like they do in the wild. Schooling is an anti-predation behavior, and most tanks don't have predators keeping the cycle of life in check.

[letoan]

None. I'll never keep them again. Got a bunch of them a few years back. They seem nice at the beginning then all they do after that is eat, poop and killing each other until 2 left.

[eatbreakfast]

I have kept Chromis atripectoralis, which look nearly identical to C. viridis, as groups for 2+ yrs without issue.

While online they cost more than C. viridis, I often see them mixed in with C. viridis and offered for the same price at local stores. As this is a positive description of C. atripectoralis dont think I am trying to sell you anything.

Any social fish will develop a hierarchy where there is posturing for dominance, so the bigger the group the more that social aggression is dispersed.

[dogface 13]

i guess i second the notion of none. lol, but if you want another variety your gonna pay way more to get kinda fillers for the tank. Mine happen to huddle around each other but i also have a ton of livestock if u have little they might not.

[ca1ore]

Originally Posted by Dmorty217

Zero... don't get one

Yep, that's where I am too. Though I do have two in my current tank (came with a CL special), they simply aren't a pretty enough fish to justify the downside.

[Deinonych]

Originally Posted by eatbreakfast

I have kept Chromis atripectoralis, which look nearly identical to C. viridis, as groups for 2+ yrs without issue.

While online they cost more than C. viridis, I often see them mixed in with C. viridis and offered for the same price at local stores. As this is a positive description of C. atripectoralis dont think I am trying to sell you anything.

Any social fish will develop a hierarchy where there is posturing for dominance, so the bigger the group the more that social aggression is dispersed.

That's a good point. C. atripectoralis usually come from Fiji, where the collection practices are typically better.