Boxfish?

[Latzi17]

I have a 10 gallon tank at the moment, and my tank has 1 sebae and 1 yellow boxfish. For some reason my boxfish likes sleeping on the water suction place on my filter. I'm not sure what to do, is this bad?

Thanks

[zhenjw]

I've heard bad stories about boxfish and related species dying, releasing their toxins from their gall bladders and killing off whole tanks. And the toxin doesn't just go away, it remains in your filter, sand, live rock, etc. Hopefully your fish is healthy ;P

[Vitaly]

I had a Yellow Polka-dot Boxfish a long time ago and absolutely loved him. They are very personable and charming fish, however, they are not good beginner fish.

As I am sure you are aware, they are not the strongest swimmers (relative to damsels, dottybacks, wrasses, etc). My concern is when you say that the Boxfish "likes sleeping on the water suction place on my filter."

Is he getting sucked into/against the intake? Do you see any signs of trauma (discoloration, abrasions, etc)? Boxfish are scaleless fish (this is particularly important when medicating) and are therefore more vulnerable to abrasion, trauma, infection, etc. If the boxfish is being suck onto the filter intake...then you need to address this immediately to prevent stress and death of the boxfish. This may require you to install a guard/shield on the intake that will keep the boxfish away from the intake.

Second you are hopefully aware of the fact the boxfish will grow to be large; anywhere from 10-14 inches depending on the source you use. Thus, the 10 gallon tank is not an appropriate "long term" home for your boxfish.

Finally, zhenjw is correct that Boxfish produce a toxin, known as Ostracitoxin that will cause the lysis/rupture of fish blood cells.¹ Generally, most people report toxicity issues when their boxfish is stressed from infections or tankmates. Be very conscious of this fact when you move the boxfish to a larger tank and plan to add new fish. They should all be peaceful, "slow moving and not too boisterous. This will reduce the stress to the boxfish and limit competition for food (they really are pretty pathetic swimmers).

Hope that helps...good luck!

1. Ostracitoxin: An Ichthyotoxic Stress Secretion of the Boxfish, Ostracion lentiginosus
http://links.jstor.org/sici?sici=0045-8511%2819690603%293%3A1969%3A2%3C335%3ATSSOTB%3E2.0.CO%3B2-T&size=LARGE&origin=JSTOR-enlargePage