Green Chromis cause mass death????

[stephicozar2]

3 foot tank - 120 litres
2 clowns
1 blue stripe cleaner wrasse
1 humbug damsel
2 green chromis
5kg of live rock so far

Up until today, 1 royal dottyback

1 year old tank
Ammonia = 0
Nitrate = 5-10
Biolife filter

I got 5 chromis the week before Christmas. I lost 3 within a week. This morning my dottyback (1 year old) was just dead on the bottom of the tank with no prior warning.

Now my humbug is looking really lethagic, not eating (I don't think he's eaten anything for 24 hours).

One of my clowns, the female, has what looks like a pimple on her chin. I've been using some fishy medicine periodically for this for about 2 months and it comes and goes.

Any ideas what is causing my tank to suddenly be so sick when I haven't had any fatalities in the year its been operational?

 

[Lotus]

Welcome to the site

Have you taken readings for salinity, ammonia and nitrates?

My guess is that the medication has killed off your biofilter, or in other ways affected your tank. What kind of medication is it?

I'd also add that I think you tried to add too many fish to a small tank at one time, which probably caused a big enough ammonia spike to kill some fish and sound the death knell for others. You only have a small amount of live rock in your tank, which would also limit your bioload.

 

[stephicozar2]

Thanks for the reply.

Ammonia and Nitrate were perfectly normal - one week after the last water change and with the dead dottyback... Ammonia = 0 and Nitrates were 5.

My salinity is a liiiiiittle low but still very close to normal.

The medication was API Melafix. I was using a reduced dose but the instructions do say to remove the activated carbon if possible, which I didn't do.

My humbug still won't eat anything, he's usually first in the chow line but now he doesn't want a bar of it - just swims right by.