Saltwater Aquarium/New Fish Dying


I have a 75g tank that has finished its cycling quite awhile ago.  I had the tank running for about 4 yrs prior and took it down at the beginning of summer when some sort of disease got into it.  Got it back going about 2 months later with my original emerald crabs, hermits, snails and the only fish I had left from the disease - humu humu trigger.  After about a month of it running, everything was looking good until my trigger got caught up in a hose that lost it's strainer (my mistake!).  Today, about a month after the trigger died, I finally decided to buy some more fish.  They all came in fine.  About 2 hours into the acclimation period (drip method), a couple of them started to look bad (breathing heavy, laying on their side, etc.).  By time I got them to the tank, most were already laboring and died.  The clown lasted about an hour before acting erratic and dying.  I kept 2 others - a green dragonet and trigger - in a bag after acclimation because of what happened to the others.  Once I put the dragonet in the water, it acted fine but then started acting up and dying.  I'm now about 8 hours into it and only have the trigger left, which I have been holding in the bag floating at the top of the tank swapping the water in the bag with aquarium water every 15 minutes.  I don't want this one to die.

I've checked everything before putting the fish in and after; all tests come out normal.  Even compared the tank water to the water the fish came in and they have the same readings.  All other items in tank are fine - shrimps, hermits, star, anemone, snails, crabs, etc.  Could there be a toxin in my water that is killing the fish?  I can't stand losing fish - it's not the money as much as the wastefulness or my ignorance.  Do you have any ideas or suggestions on what I should do next?

Thank you kindly for your help!

Hi Tim:

Sorry to hear of this misfortune.

Unfortunately I would not, "with any certainty" be able to diagnose what is going on with your aquarium fish. I would ask your local fish store that you purchased the fish from, if they quarantine their fish first, before selling them. I would also ask them if they experienced what you are experiencing with any of their fish. Perhaps there is a parasite that is the root cause...

I would also recommend to check for Ammonia in your water, often times fish will act erratically when there is Ammonia present. Your Ammonia level should always read "zero", on most Ammonia test kits sold for measuring Ammonia in aquariums.

Also, I would strongly advise you to quarantine all new fish for at least 3 to 4 weeks, before adding them to your resident fish tank.

I wish you luck with all your future saltwater aquarium endeavors.

Happy New Year!


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David Ocreef


Technical saltwater coral reef related aquarium questions are welcome. Coral, invertebrate, and peaceful species of saltwater fish questions are welcome. Questions asked on Saturday and Sunday will be answered the following Monday. REMINDER: Please check the answers pool to see if your question has already been asked and answered. Questions typically are answered within a 48 hour period, however sometimes it may take longer.


I possess over twenty-five years of hands-on experience and knowledge in the ecology of aquariums. Beyond the traditional, I have successfully tested and sustained environments that have been uncharted territories for hobbyists, for decades. I am the first to admit I don't know it all because there will always be something new, amazing, and exciting to learn about, as discoveries are made. It's a hobby one can never outgrow, or grow tired of.

MASNA - Marine Aquarium Society of North America. Director of Orange County Reef Aquatics -

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After High School, my experience and love of marine animals influenced me to take up studies in Marine Biology. Throughout college, I studied Microbiology with an emphasis on Marine Life, as well as numerous other sciences. I continued to advance in this hobby, by building a dozen or more saltwater ecosystems all utilizing Microbes as the major source of my filtration method.

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