Fish Dying Sequentially... Please help!

[cyniemay]

Hi all! I started reef keeping in March 2026, and am now experiencing concerning fish deaths. Im looking for advice or intel of what may be happening...

60 gal DT with 20 gal sump
Salinity - 1.025
N - 1.1
Phos - .19
Alk - 7.5
Calc - 420
Mag - 1200
Ammonia - 0

Water parameters remain stable, we are slowly working to raise our N and Mag.

We have a mixture of rfas, softies, lps, and a few sps. All anenomes and corals are doing fine.

Fish (how long it has been in the tank)
Pajama Cardinal (7 months)
Royal Gramma (6.5 months)
Purple firefish (6 months)
Phantom Snowflake Clown (3 months)
Mocha Storm Clown (3 months)
Possum wrasse (2 months)
Leopard wrasse (1 month)
2 Bangai Cardinals (1 month)

I havent seen any signs of tank aggression.

So... 4 weeks ago I added the bangais and leopard wrasse after a slow drip acclimation. They were all doing well for 1 week, then one bangai started breathing heavy, laid on the sand, and died with no warning. The fish did not have any visible spots or marks, and was eating right up to its death. We fed it to the rfa's and removed whatever wasnt eaten.

One week later, the other bangai also died under the same circumstances. I removed the fish within 5 minutes of its last breath. We chalked it up to delayed acclimation stress and cut our losses, but then my beloved phantom snowflake clownfish passed away 5 days later.

The day before my clownfish died, I remember her poops looking stringy and maybe a bit clear and her tummy was plump. The day of her death (oct. 25) was maintenance day. We did a routine 5 gallon water change and dosed for our ph. She ate breakfast and dinner as normal and didnt show any signs of anything being wrong. When we were turning in for the night we found her dead and being eaten by the cuc. Her organs inside her tummy appeared to be black. We removed her right away.

5 days later, my royal gramma didnt eat dinner, and did not eat again. She was hiding in the back of the tank in a cave, and would not eat even when we target fed a few pieces of mysis. Her breathing seemed a little labored. We immediately added an airstone to the sump, increased water surface agitation, and started a 2.5 day tank blackout. During the blackout, she seemed to get a tiny bit better, but would immediately hide when I would try to look at her. It almost seemed like she was scared of me.

That brings us to today... my royal gramma just passed away. Immediately upon death we did a 5 minute fresh water bath, and did not see any flukes.

Any advice on how to proceed is greatly appreciated. I am completely heartbroken and just want to make sure the rest of my fish are safe and healthy, but I do not know what has taken the lives of my other fish as there were no visual signs of flukes, velvet, or ich on any of them.

I'm happy to provide any other information you may need. Thank you in advance.

 

[vetteguy53081]

Hi all! I started reef keeping in March 2026, and am now experiencing concerning fish deaths. Im looking for advice or intel of what may be happening...

60 gal DT with 20 gal sump
Salinity - 1.025
N - 1.1
Phos - .19
Alk - 7.5
Calc - 420
Mag - 1200
Ammonia - 0

Water parameters remain stable, we are slowly working to raise our N and Mag.

We have a mixture of rfas, softies, lps, and a few sps. All anenomes and corals are doing fine.

Fish (how long it has been in the tank)
Pajama Cardinal (7 months)
Royal Gramma (6.5 months)
Purple firefish (6 months)
Phantom Snowflake Clown (3 months)
Mocha Storm Clown (3 months)
Possum wrasse (2 months)
Leopard wrasse (1 month)
2 Bangai Cardinals (1 month)

I havent seen any signs of tank aggression.

So... 4 weeks ago I added the bangais and leopard wrasse after a slow drip acclimation. They were all doing well for 1 week, then one bangai started breathing heavy, laid on the sand, and died with no warning. The fish did not have any visible spots or marks, and was eating right up to its death. We fed it to the rfa's and removed whatever wasnt eaten.

One week later, the other bangai also died under the same circumstances. I removed the fish within 5 minutes of its last breath. We chalked it up to delayed acclimation stress and cut our losses, but then my beloved phantom snowflake clownfish passed away 5 days later.

The day before my clownfish died, I remember her poops looking stringy and maybe a bit clear and her tummy was plump. The day of her death (oct. 25) was maintenance day. We did a routine 5 gallon water change and dosed for our ph. She ate breakfast and dinner as normal and didnt show any signs of anything being wrong. When we were turning in for the night we found her dead and being eaten by the cuc. Her organs inside her tummy appeared to be black. We removed her right away.

5 days later, my royal gramma didnt eat dinner, and did not eat again. She was hiding in the back of the tank in a cave, and would not eat even when we target fed a few pieces of mysis. Her breathing seemed a little labored. We immediately added an airstone to the sump, increased water surface agitation, and started a 2.5 day tank blackout. During the blackout, she seemed to get a tiny bit better, but would immediately hide when I would try to look at her. It almost seemed like she was scared of me.

That brings us to today... my royal gramma just passed away. Immediately upon death we did a 5 minute fresh water bath, and did not see any flukes.

Any advice on how to proceed is greatly appreciated. I am completely heartbroken and just want to make sure the rest of my fish are safe and healthy, but I do not know what has taken the lives of my other fish as there were no visual signs of flukes, velvet, or ich on any of them.

I'm happy to provide any other information you may need. Thank you in advance.

With the corals doing well and I assume inverts, this points to disease and not water issue. Were any of the deceased fish found with their mouths open?
The signs of heavy breathing and loss of appetite suggest a gill disease issue in which I suspect flukes

 

[Uncle99]

Parasites don’t always show themselves.
Most common 1 by 1 killer in reef aquaria is ick.
Can’t say for sure but the process of fish dies, then another, then another sure mimics this.

 

[cyniemay]

With the corals doing well and I assume inverts, this points to disease and not water issue. Were any of the deceased fish found with their mouths open?
The signs of heavy breathing and loss of appetite suggest a gill disease issue in which I suspect flukes

The royal gramma's mouth was open, but the other fish were not.

Would you recommend a round of prazipro to be safe?

 

[cyniemay]

Parasites don’t always show themselves.
Most common 1 by 1 killer in reef aquaria is ick.

Ich or velvet was a cause we pondered... but the deaths are spread out? Wouldn't ich or velvet rapidly kill all fish in the tank within 72 hours?

 

[Uncle99]

Ich or velvet was a cause we pondered... but the deaths are spread out? Wouldn't ich or velvet rapidly kill all fish in the tank within 72 hours?

Velvet yes, death is 24-36 hours, maybe 48 best case.

But Ick nope, the parasite doesn’t really want the fish to die as it feeds on them, when the fish dies, the parasite loses its host and unfortunately after days and days, the fish due to stress and lack of food, succumb to the ick.

We had fish go 5 days to 2 weeks before death, it’s quite dependent on the fish.

And with ick,it doesn’t always kill every fish. That’s a myth. It can, but that’s not a for sure.

Some fish may have some immunity or have such a good slime coat that parasites can’t attach.

The Mandarin fish is one example. It seems to resist infection more than say a blue tang.

 

[cyniemay]

This was the 2nd bangai post mortem

 

[cyniemay]

Velvet yes
Ick nope, the parasite doesn’t really want the fish to die as it feeds on them, unfortunately after days and days, the fish due to stress and lack of food, succumb to the ick.

We had fish go 5 days to 2 weeks before death, it’s quite dependent on the fish.

And with ick,it doesn’t always kill every fish. That’s a myth. It can, but that’s not a for sure.

Some fish may have some immunity or have such a good slime coat that parasites can’t attach.

Fascinating, and very good to know!

Do you have any experience with reef safe treatments? Maybe seachem focus + metroplex? If it isn't this, would giving the surviving fish medicated food be wise? Im unsure of my next step.

I do not currently have a quarantine tank, but have one i could set up. I would just hate to lose another life while waiting for it to cycle.

 

[Uncle99]

This was the 2nd bangai post mortem

Unfortunately that fish would be hard to see ick on.

 

[Uncle99]

Fascinating, and very good to know!

Do you have any experience with reef safe treatments? Maybe seachem focus + metroplex? If it isn't this, would giving the surviving fish medicated food be wise? Im unsure of my next step.

I do not currently have a quarantine tank, but have one i could set up. I would just hate to lose another life while waiting for it to cycle.

There are no in tank treatments that will solve ick. There are many who claim they do, but don’t be fooled.

Only 30 days coppersafe (or equivalent) in isolation along with 60 days of no fish in your DT will work.

I can’t say for sure what your dealing with becuase I can’t see any…..but possible….ick is the most common parasite we run into.

Food supplements to me are useless.

Ick doesn’t always kill every fish.

It got only 4 of my 14 and then just ended. Perhaps just lucky.

We had no way to remove them, so no choice.

But copper does work if done corrrctly.

 

[vetteguy53081]

The royal gramma's mouth was open, but the other fish were not.

Would you recommend a round of prazipro to be safe?

Ick would have been highly visible with associated behaviors and would take a few days. Signs point to Gill issue and I dont suspect velvet and Yes PtaziPro can be used and you want to dose at 85% of recommended and allow it to work for 7 days, change water and apply one more application lasting 7 days and do add an air stone as Prazi lowers both oxygen and appetite which may be the case or part of it

 

[Uncle99]

@vetteguy53081 is posting no way ick, so always go with the experts advice.

Ick is usually white to white grey dots that appear, then disappear, around 4 ish days, then reappear more each time, this cycle continues, over and over until death. Fins are a good place to,look for them.

The fish stops eating, may scratch or rub itself to try to get some relief, and breath heavy.

 

[Mr. Mojo Rising]

Can we see a full tank picture? Sometimes it gives good clues

 

[Jay Hemdal Verified Community Expert]

Hi all! I started reef keeping in March 2026, and am now experiencing concerning fish deaths. Im looking for advice or intel of what may be happening...

60 gal DT with 20 gal sump
Salinity - 1.025
N - 1.1
Phos - .19
Alk - 7.5
Calc - 420
Mag - 1200
Ammonia - 0

Water parameters remain stable, we are slowly working to raise our N and Mag.

We have a mixture of rfas, softies, lps, and a few sps. All anenomes and corals are doing fine.

Fish (how long it has been in the tank)
Pajama Cardinal (7 months)
Royal Gramma (6.5 months)
Purple firefish (6 months)
Phantom Snowflake Clown (3 months)
Mocha Storm Clown (3 months)
Possum wrasse (2 months)
Leopard wrasse (1 month)
2 Bangai Cardinals (1 month)

I havent seen any signs of tank aggression.

So... 4 weeks ago I added the bangais and leopard wrasse after a slow drip acclimation. They were all doing well for 1 week, then one bangai started breathing heavy, laid on the sand, and died with no warning. The fish did not have any visible spots or marks, and was eating right up to its death. We fed it to the rfa's and removed whatever wasnt eaten.

One week later, the other bangai also died under the same circumstances. I removed the fish within 5 minutes of its last breath. We chalked it up to delayed acclimation stress and cut our losses, but then my beloved phantom snowflake clownfish passed away 5 days later.

The day before my clownfish died, I remember her poops looking stringy and maybe a bit clear and her tummy was plump. The day of her death (oct. 25) was maintenance day. We did a routine 5 gallon water change and dosed for our ph. She ate breakfast and dinner as normal and didnt show any signs of anything being wrong. When we were turning in for the night we found her dead and being eaten by the cuc. Her organs inside her tummy appeared to be black. We removed her right away.

5 days later, my royal gramma didnt eat dinner, and did not eat again. She was hiding in the back of the tank in a cave, and would not eat even when we target fed a few pieces of mysis. Her breathing seemed a little labored. We immediately added an airstone to the sump, increased water surface agitation, and started a 2.5 day tank blackout. During the blackout, she seemed to get a tiny bit better, but would immediately hide when I would try to look at her. It almost seemed like she was scared of me.

That brings us to today... my royal gramma just passed away. Immediately upon death we did a 5 minute fresh water bath, and did not see any flukes.

Any advice on how to proceed is greatly appreciated. I am completely heartbroken and just want to make sure the rest of my fish are safe and healthy, but I do not know what has taken the lives of my other fish as there were no visual signs of flukes, velvet, or ich on any of them.

I'm happy to provide any other information you may need. Thank you in advance.

The FW dip on a deceased fish will only show one species of fluke, you would need a microscope to see the other types. However, if you had flukes severe enough to kill these fish, you would have seen flashing/scratching.

Were the cardinals wild caught? There is a species-specific virus that causes huge mortality in those.

I’d like to see a video of the tank and remaining fish ….