Keeping a school of chromis?

[CrunchyBananas]

I'm looking at a tank upgrade to a much larger tank, and I've always wanted to have a larger (20+) school of green chromis.
The issue is, every time I've tried groups of them (3-5) over the years, they inevitably whittle themselves down to 1 Alpha Chromis.
Has anyone had luck keeping a school? I'm hypothesizing a large enough school can dissipate the aggression enough for them to live long term.

Is this sort of a lost cause? Is the aggression inevitable at any size school?

 

[Sean Clark]

I want to do the same thing. I had a small group before and wound up with one as well. I was thinking 19, 23, or 29 to make a nice prime number group.

 

[Zach B]

I started with 6 about 2 years ago, down to 3. It'd be nice if they wouldn't kill each other off but it seems likely it will eventually happen. Best of luck

 

[bushdoc]

Same here, additionally they are prone to Uronema, so be sure to properly quarantine them before putting into DT.

 

[Sean Clark]

I wonder if there is a point where the number of fish helps keep the aggression spread out among the group and they actually survive and will maintain their numbers.

 

[Zach B]

I wonder if there is a point where the number of fish helps keep the aggression spread out among the group and they actually survive and will maintain their numbers.

I'm sure it could as well as tank size. Good point

 

[bushdoc]

I wonder if there is a point where the number of fish helps keep the aggression spread out among the group and they actually survive and will maintain their numbers.

Good question, it has been asked on forums here. It works for Freshwatr cichlids, but doesn't seem to work for most if any type of saltwater fish.

 

[Zach B]

It absolutely helps with big fish like tangs. Having 3 in a large enough tank is often better than 2

 

[Zach B]

Aggression spread as stated

 

[JM302]

I firmly believe if you can keep a steady flow of food in the tank you can have long(er) term success. I'm in the process of testing hourly feeding via an Avast Marine Plank. I'm feeding a cocktail of freeze dried food. So far the they're all getting along - only time will tell though. In my experience, if they're full, aggression is minimized.

 

[Matty Ice]

I thought I read somewhere it’s possible to have higher numbers of them if there’s a few other aggressive fish in the tank to keep them “helping” each other school

 

[Fishfreak2009]

Frequent feeding and larger numbers of healthy fish should do fine. I think a lot of the aggression people attribute to chromis death is actually uronema causing missing scales and bloody wounds. Shredded fins from the fish trying to itch themselves.

My group of 4 do just fine in my 4' 75 gallon being fed 4-6x daily, and I plan on adding another 5 when it is upgraded to the 5' 100 gallon. My old 380 gallon had 15 greens, 5 bicolor, 7 vanderbilt, and a wide variety of other planktivores (anthias, staghorn damsels, fairy and flasher wrasses) and other larger fish like angels, tangs, and triggers, and I had no losses from aggression in there either.

Fwiw, I started with 5 in my 75 gallon, and only lost 1 because it got sucked through the overflow and I didn't have the filter socks in place, so it went through the protein skimmer pump

 

[Miami Reef]

I had and still have 12. It’s coming close to the 1 year mark and I haven’t lost one.

I attribute that to my large tangs and lamarck angel. The more bigger and scarier the other resident fish, the less likely the chromis will kill each other off.

 

[Sebastiancrab]

I firmly believe if you can keep a steady flow of food in the tank you can have long(er) term success. I'm in the process of testing hourly feeding via an Avast Marine Plank. I'm feeding a cocktail of freeze dried food. So far the they're all getting along - only time will tell though. In my experience, if they're full, aggression is minimized.

I am convinced extra daily feedings for more than one chromis is the answer to reducing aggression. I think they could eat all day based upon their behavior.

 

[Pneumatic_Addict]

Keiji Oda is somewhat active on Polo Reef and Ask BRS on FB pages. He’s got a group of 100x in a larger SPS tank. Maybe shoot him a message?

From what I’d guess, his success is probably owed somewhat to the many large SPS colonies (natural shelter) and his larger Angels/Butterflies, as mentioned above.

 

[ISpeakForTheSeas]

My understanding is that keeping a large school can theoretically work, but - as mentioned above - there are a number of things to keep in mind with schooling:

- The number of schooling fish in the tank (I've heard odd numbers are preferred, and the preferred number of fish that I've seen seems to be 9 to 11 at a minimum; the more fish, the more diluted the aggression is between them)

- The size of the tank (for quality of life purposes for your fish, bigger is better - yes, some animals will be calm when shoved into tiny spaces with large numbers of conspecifics where if there was just one or two conspecifics, it would be a deathmatch, but they obviously wouldn't be happy in that situation long-term)

- The amount fed, the quality of the feed, and the frequency of feedings (basically more food = less aggression; and better food = better health = happier, less aggressive fish [theoretically])

- Tankmates (big, scary tankmates that the schooling fish could view as a threat may act as an outside force that keeps the schooling fish focused on not getting killed rather than on fighting amongst themselves)

- The scape of the tank (lots of fish need lots of places to hide/sleep - the more hiding places, the safer the fish feel; line-of-sight-breaks can also help with feeling safe)

That's all I've got for the moment (and pretty much all of it has been mentioned above), but basically - to my understanding - it's a balance of making the fish feel threatened enough by external sources to prevent infighting while also making them feel safe enough (largely through their numbers, the tank's scape, and food security) to not be too stressed. If you're able to strike that balance, you should be able to see schooling behavior (to the best of my current understanding).

 

[CrunchyBananas]

This is all great input, thank you everyone! My plans of attack were: large (quarantined) group and frequent feedings. I think I’ll add some more aggressive larger fish (perhaps a clown tang) to keep them schooled, shoot for prime numbers, and plenty of smaller hiding spots for them.

 

[SteveMM62Reef]

I highly recommend one of these if you are going to keep a School of any kind of fish. Cuts down on the Aggression. Available on Amazon. I have three, for my various tanks, other than one received smashed, not a bit of problem with them. Great for vacations, too.

Petbank Automatic Fish Feeder - Rechargeable Timer Fish Feeder with USB Charger Cable, Fish Food Dispenser for Aquarium or Fish Tank​

BTW, We had an Auto Feeder for our Cat, only took him a couple of days, watching us, to figure out how to get it to feed on demand.

 

[CrunchyBananas]

I highly recommend one of these if you are going to keep a School of any kind of fish. Cuts down on the Aggression. Available on Amazon. I have three, for my various tanks, other than one received smashed, not a bit of problem with them. Great for vacations, too.

Petbank Automatic Fish Feeder - Rechargeable Timer Fish Feeder with USB Charger Cable, Fish Food Dispenser for Aquarium or Fish Tank​

BTW, We had an Auto Feeder for our Cat, only took him a couple of days, watching us, to figure out how to get it to feed on demand.

Absolutely, an auto feeder is a must with this I believe, might splurge and get the avast marine plank!

 

[chipchipmofo]

a friend inteoduced 50 chromis at once and havent had any problems as of what I know..

bad pic but that was his new tank a few months ago. 3000 Litres