Just how toxic are boxfish?

[ss88]

I have an adult Scrawled cowfish Acanthostracion quadricornis. He has been in my fish quarantine system since January. Doing rather well eating most prepared foods. I’m planning on moving him out into one of my other Aquariums, just how toxic are these fish should something unfortunate happened to him? Can they really nuke a tank?

 

[Slocke]

The toxin, pathutoxin, is similar to the toxin of sea cucumbers. I’ve heard of several people keeping them and I’ve yet to hear of a tank being nuked by one even when one has died in the tank. Though they can be a bit tricky in terms of care apparently.

@ISpeakForTheSeas have any good info to add?

 

[PharmrJohn]

Cow fish releasing toxins, true or false?

I recently acquired a scrawled cow fish, and have read many posts saying cow fish release toxins that will crash your tank, and others that say they won’t. Some people have had them die in their tanks and not have any affects. My question is, where does this myth originate from? Why has this...

www.reef2reef.com

It's a thread on this subject from 2021.

 

[Slocke]

Cow fish releasing toxins, true or false?

I recently acquired a scrawled cow fish, and have read many posts saying cow fish release toxins that will crash your tank, and others that say they won’t. Some people have had them die in their tanks and not have any affects. My question is, where does this myth originate from? Why has this...

www.reef2reef.com

It's a thread on this subject from 2021.

Uggh that thread seems like a mess of people who don’t know what they are talking about.

1. Yes they can definitely release a toxin (though that doesn’t mean they will or even that it is likely)

2. Puffer fish cannot release a toxin into water and nuke a tank. The toxin in pufferfish is released only by consumption of certain organs. I mean they aren’t even that closely related…

 

[vetteguy53081]

I have an adult Scrawled cowfish Acanthostracion quadricornis. He has been in my fish quarantine system since January. Doing rather well eating most prepared foods. I’m planning on moving him out into one of my other Aquariums, just how toxic are these fish should something unfortunate happened to him? Can they really nuke a tank?

Its a low level secretion labeled as toxin and rarely emitted when fish is threatened and is released via the plates of its body.

 

[ISpeakForTheSeas]

The toxin, pathutoxin, is similar to the toxin of sea cucumbers. I’ve heard of several people keeping them and I’ve yet to hear of a tank being nuked by one even when one has died in the tank. Though they can be a bit tricky in terms of care apparently.

@ISpeakForTheSeas have any good info to add?

Some, yes.

For the toxin:

Just to clarify here, boxfish/cowfish actually have to be alive (and stressed) to produce their toxins - they can't physically produce the toxins when they're dead.

No experience with keeping them myself, but, for boxfish specifically, these guys aren't toxic when they die, they're only toxic when alive and stressed (they have to be alive to produce the toxin, and they only produce it when stressed). The toxin they produce is a potent ichthyotoxin called Ostracitoxin or Pahutoxin (ichtythoxin meaning it's a toxin that primarily effects fish, though this toxin has been demonstrated to slowly affect a wide variety of inverts too). In small quantities, the effects may be mild as long as the toxin is promptly removed, but the effects of it on fish are irreversible (meaning the fish - if they heal from it at all - will recover over a long period of time, and they will only recover if the damage is mild and the toxin is no longer present in their environment).

When the toxin is present even at 5ppm in the water (the equivalent - if my math is right - of ~3.4ml of the toxin in a 180 gallon tank), 50% of the following species of fish died within the following times*:
Abudefduf abdominalis - 6 minutes
Acanthurus sandvicensis - 8.5 min
Kuhlia sandvicensis - 10 min
Mugil cephalus - 12.5 min
Mollienesia litpinna - 15 min
Bathygobius fuscus - 30 min

Given that the damage is irreversible and lethal even at relatively small doses (and that boxfish themselves aren't immune to the toxin, though they are more resistant to it than other fish), I'd guess it's probably not an overblown risk (though it is something you could likely try to prepare for by running carbon and having a water change and QT ready at all times).

That said, I don't know how fast these guys produce the toxin, but as long as the fish doesn't get too stressed, it should theoretically never produce enough toxin to cause an issue (though I'd constantly run carbon on the tank just to be safe).

* The study I pulled the data from:

Toxic Stress Secretions of the Boxfish Ostracion meleagris Shaw on JSTOR

Donald A. Thomson, Toxic Stress Secretions of the Boxfish Ostracion meleagris Shaw, Copeia, Vol. 1969, No. 2 (Jun. 3, 1969), pp. 335-352

www.jstor.org

For anyone scared by the numbers in the quote above:

I’ve kept various box fish over the years. The only time I’ve had issues with toxins were with boxfish I had just caught myself and placed in buckets on the boat.
That said, this is one of those fish that appear to do fairly well, but asking who has kept one longer than two years, not many hands in the air. The only ones I have had long term success with were temperate Australian species.

Jay

I also haven't heard of any confirmed "nukes" by these fish; as you said, the risk is there, but given a decent environment, the risk seems to be quite low.

For care, the threads below likely aren't perfect guides, but they may be helpful:

Box & Cowfish - What You Need to Know

So, let talk about the adorable yet largely misunderstood Cowfish & Boxfish. Before I begin, let me say that I’m NOT an expert, I’m not a marine biologist and everything I’m sharing is based on very real personal experience. I’m going to group these two fish (Cow & Boxfish) together, as I find...

www.reef2reef.com

Longhorn cowfish discussion and thoughts.

Hopefully I will get some insight from those with experience. First, I have one. I bought this little guy about the size of a half dollar about July 22nd 2023. So it is now 1 year old in my care. And boy has it grown with a lot of growth yet to come!! It is now 6”-7”. From tip to tip. I...

www.reef2reef.com

Like with many expert-only critters, proper feeding seems to be one of the keys to keeping these; these do have the added difficulty of it being hard to tell if they're getting enough to eat due to their bone structure though. I would guess keeping them low stress is also important, as they are vulnerable to their own toxins, so even if they only secrete very small amounts at a time (small enough not to harm the other tank inhabitants) it could potentially slowly kill them.

So, feed them well (they reportedly eat basically anything except cnidarians - corals, nems, hydroids, etc. - in the wild, so variety including a good mix of algae is probably wise) and keep them relaxed is my (vague) advice at this point until I find something more concrete to go with.