30 chromis in a 500g.

oskar reef · Jul 24, 2017

hi, question is 30 chromis too many in a 500g tank????
tank is not set up yet just trying to decide how many can i put.. i know they will kill one by one eventually but i plan keep adding as they disappear...hopefully it doesn't come to that. i have learn that they become more aggressive if you hardly feed or once a day.. so planing on having an auto feeder 4x small portions per day . Question is, does any one have that many in their tank?? i research but big school only comes up with something like 5-8... thanks in advance..( i will have enough filtration for that many fish plus more)

sbash · Jul 24, 2017

Looking at video below, it seems possible. It is a 300 gallon, and they so not appear to be shoaling or schooling... You might see some shoaling in a 500 though... I have one in my 220, it is pretty big so I am not going to add more until he passes away. At that point, I will only be going with five to eight...

From what I have researched; multiple feedings per day (as you have said) as well as lots of hiding places for night will help keep them from killing each other...

madehtsobi0109 · Jul 24, 2017

I have 9 in a 400 for almost half a year now... they shoal together most of the time and are not shy at all. Some chasing here n there

snappa1953 · Jul 24, 2017

Another thread pointed to an Advanced Aquarist article which showed that they are reef fish not schooling fish. They need multiple daily feedings and many hiding places to survive in a tank.

Maybe worth investing in a top quality autofeeder.

eatbreakfast · Jul 25, 2017

It should work. The multiple feedings will help. Enough hiding places and high flow also help.

oskar reef · Jul 25, 2017

sbash said:
Looking at video below, it seems possible. It is a 300 gallon, and they so not appear to be shoaling or schooling... You might see some shoaling in a 500 though... I have one in my 220, it is pretty big so I am not going to add more until he passes away. At that point, I will only be going with five to eight...

From what I have researched; multiple feedings per day (as you have said) as well as lots of hiding places for night will help keep them from killing each other...

thanks for the video. that looks awesome ....

jrwoltman · Jul 25, 2017

I had 8 in my old 75. You will be fine.

oskar reef · Jul 25, 2017

i think they need some kind of treat for them to school...
i will have 5-6 very large tangs , i think it will make them school. even if they dont school with so many it will look like they are... lol

Gweeds1980 · Jul 25, 2017

Not talking about chromis here, but schooling in general. My 320g used to be FW... I was determined to have some proper schooling behaviour.

After lots of research I found that the schooling response will disappear if there is no perceived threat... ie it is purely for safety in numbers, no other reason. In FW schooling fish you normally need at least 50 fish and something big that is perceived as a threat... it needs to be the right shape too (I discovered a 2ft plec didn't work).

I ended up with a school of 120 odd Buenos Aires tetras alongside spotted metynnis (look a lot like piranha)... that didn't really work either as piranhas don't normally tackle live fish, so weren't perceived as a threat. I happened to have another tank sited about a foot away, in which was an Oscar. I added to this second tank two peacock bass to grow out and sell on... The second they were in there, all the tetras schooled constantly!

I ended up adding 4 bala sharks (right shape, not from the same region so no innate response that they are veggies). The school kept together and moved as one, an amazing sight.

So, I digress, I'd suggest that to get the schooling response, you'll need something more than a big tang... The chromis will recognise them and their shape as not being a threat.

In a 500g, how about a bamboo cat shark? Assuming dimensions are good, that should elicit a schooling response.

Interestingly, when the fish are schooling, aggression reduces (basically they're all concentrating on not getting eaten) so you may be able to maintain a school of 50 without them picking each other off.

sbash · Jul 25, 2017

Gweeds1980 said:
So, I digress, I'd suggest that to get the schooling response, you'll need something more than a big tang... The chromis will recognise them and their shape as not being a threat.

Perhaps if you just stuck your hand in and stirred the water a few times a day?

All kidding aside; and this is just a thought, I am not much for fish psychology... Rather than 'large' fish, maybe a carefully selected few semi-aggressive fish would do it?

Gweeds1980 · Jul 25, 2017

sbash said:
Perhaps if you just stuck your hand in and stirred the water a few times a day?

All kidding aside; and this is just a thought, I am not much for fish psychology... Rather than 'large' fish, maybe a carefully selected few semi-aggressive fish would do it?

Depends... if they are aggressive because they're defending territory... like damsels, it won't work. If the are aggressive because they want to eat the chromis, then it will work... problem there is that the chromis will probably get eaten!

Piscivorian fish tend not to be aggressive... they don't need to be. They travel and hunt normally, rather than defend a territory. It's the territorial fish which are aggressive, which on the reef tends to be herbivores defending their algae patch (eg tangs) or the plaktonivores (e.g. anthias) which are defending the richest feeding grounds.

It's why we can swim with sharks, but my humbug damsels attack me when I put my hand In!

The trick in getting a schooling response is to have a fish which the chromis will perceive as a threat to life, but that we know won't hurt them...

Possibly one of the crustacean eating morays, cat shark. Or anything which practices Batesian mimicry such as the marine Betta (Calloplesiops attivelis) might work.