Fish dying - no idea why.

[colettem]

Very disheartened - looks like my third fish is about to die. I wonder if anyone has any suggestions about what I can do to save the other two that are left.

The story is as follows - sorry it's a bit longwinded but don't want to miss out anything crucial:

Feb 14th - buy 5 small green chromis (my first ever marine fish)and put them in my 13 gallon QT. This has a sponge filter, a BB, some hiding places made out of pipe, a small powerhead and is fully cycled. Initially they seemed to be fine.

About two weeks after introduction I notice the smallest green chromis is looking a bit unwell - nothing very specific and nothing external to see apart from possibly a tiny white spot two days earlier (difficult to know for sure as they never keep still). This fish died after a few hours. I decided that the most likely diagnosis was ich even though there were no white spots visible when he died. Decided to treat with hyposalinity of 1.012.

Ten days later fish number two suddenly looks unwell and in a matter of hours is dead - again no specific symptoms.

Now three weeks after the last death (just as I'm thinking about beginning to raise the salinity) a third fish is looking in extremis - again no external signs of disease but I had noticed hadn't been feeding as voraciously as the others for the past couple of days. He has fast gill movements but not surface gasping. The other two fish look fine.

Current parameters:
pH 8.2
Sal 1.011
Amm and nitrite 0.

Anyone got any clues as to what is going on? I'm stumped as there doesn't seem to be any external evidence of disease. Although I've never seen any definate bullying going on and there is no evidence of trauma, I wonder whether the biggest two fish could be harassing the ones that have died . I've been reluctant to use copper firstly as I don't know what I'm treating and know it can be toxic; and secondly I would like to use this tank in the future for inverts.

At the moment the sick fish is in a breeding net, it doesn't look like he is going to last the night. I'm very saddened as I have been trying to do everything strictly by the book and be as conscientious as I can.

Hope someone out there can help.

[Recife]

Your salinity is way too low. You should have a minimum of 1.022, with 1.024-1.026 being recommended.
Among other things, that might explain hy your fish are dying.

[Jeremy Blaze]

This is very typical of small groups or blue/green chromis.

What happens is the more aggresive one is picking on the weakest, thus killing it. Then it moves on to the next.

Many people say they are good schooling fish, but I have found this to be untrue.

You need at least 12 for the aggresion to be displaced or they will kill the smallest, or weakest.

I have had this happen in our 1200 gallon reef even when starting with 24. By 1 year there is only one left. I have talked to many others who service tanks, and they report the same.

[colettem]

Recife - 1.012 is actually the recommended level for hypo treatment which I am currently undertaking on the assumption that ich is the cause of the deaths.

Thanks Jeremy. I wondered if this was the case as there always seems to be a distinct pecking order amongst them and it has always been the smallest that dies. What a shame - one of the reasons I chose these as my first fish is that everywhere you read (and I've done lots of reading here and elsewhere) is that they are termed "peaceable" and are not meant to be nasty fish that kill each other like the other members of the damsel family.
Hope they won't start terrorising any other inhabitants of my main display when I get my next fish.

[BTTRFLYGRL]

SG Of 1.012 will not kill ich. It needs to be at 1.009

[Jeremy Blaze]

I have never had a problem with them bothering other fish.

[Agu]

IME Jeremy is right on target, chromis kill each other ruthlessly. Your scenario is exactly what I had happen in a 180.

[ratziel]

Dittos on the ruthless part. I started with 3 in a 20g and after watching the largest one harrass the other two, a month later there was only one. I call him the "Highlander" ;) I know a lot of people call them great schooling fish but I didn't have any luck with them. Also dittos on the 1.009 for hyposalinity, 1.012 may be enough to relieve some stress on the fish and help it beat ich but it takes 1.009 to kill ich.

[colettem]

The fish sadly died overnight. An external post mortem revealed no evidence of white spot or other parasites so I think the bullying theory is the most likely cause of the deaths especially given that there are clearly three of you who have posted exactly similar experiences. It's a real shame as if I'd known about this I never would have chosen these supposedly peaceful fish. I'd heard that bad things happen if they are kept in even numbers as opposed to odd numbers but it seems like any number over one is going to be unlucky!
I've been getting my parts per thousand muddled up with SG on the hyposalinity issues - 1.009 in SG and 12-14 in ppt is the correct treatment - thanks for correcting my mistake.

My plan now is to raise salinity slowly and get the remaining two into the main display to see how they fare in there. There are plenty of hiding places so hope the fish now lowest in the pecking order will survive. I will now rename the alpha male fish Christophe and maybe the other one Sean if he survives!!

[smcnally]

Did you happen to check your ammonia level in your QT tank? I would think 5 chromis is lot to put in a 13 Gal tank for an extended period of time.

[colettem]

The ammonia levels have always been OK in the tank. Unfortunately I never got to have 5 for an extended period of time!! They are actually very small - I did wonder whether they might have been a bit over crowded but compared to the tank they came from at the lfs which they shared with many others my QT was a great improvement for them. At their size there was plenty of swimming room but obviously not ideal for anything other than a quarantine period.

[ERICinFL]

I started with four Blue Chromis and now the largest is left. Only took three months.