I've kept a lot of unusual creatures in tanks and terrariums over the years, part of being an amature biologist. Bet this never happens to you straight up astronomy types.
Now there is this fish called a fresh water lion fish, Halophryne trispinosus. I don't see the resemblence myself. They looked and acted more like scorpion fish or stone fish. No toxic spines though. I checked with the folks at Steinhardt Aquarium as I had little children at the time.
I was fortunate enough to have owned 3 of them for about 2 years. A word of warning. The males sing. Really, really loud. And I had two of them. I had dueling toad fish. I also had neighbors knocking on my door wondering what that noise was.
They sound like someone playing a duck call through a sythesizer. A long weird drawn out quacking noise. They were at their worst during the summer and did I mention they only sing at night? Even with the lights on? Even during raucous football parties, (Niners!!!) or during loud poker games? "What the hell is that noise?" was a common quote at my place.
One can get by well in a 10gal tank. Get two, and you need at least a 55gal as they get along with each other like male Chipokes. I had to seperate all three of them into different tanks. The male on one side of the room would sing to the one on the other side. You could hear these things clear out to the street.
And now for the reasons to actually own them.
They are a seriously trippy, cave-dwelling, ambush predator. They are one of the few animals that have the inside of their mouths pigmented black. They use the Open The Mouth Really Wide and Use The Resulting Vacuum Method of catching prey. You have to see it to believe it. A five inch speciman about the size of a potato has a 4 to 5 inch draw. Yep, I stood by their tank with a ruler during feeding time because I was so impressed with the range of the draw.
They like a darker tank, and if you are standing in the right spot and see a goldfish "going down the tube", it looks like its spiralling into nothing, because of the black mouth, then suddenly there's this face. I'm pretty sure they are obligate piscavores as I've never seen them eat anything else.
And you really have to choose appropriate sized tank mates. Bosemoni Rainbows, full grown Scissortails and Giant Danios aren't big enough, (don't ask), even though you're sure they will be.
If you turn off all the lights and shine a pen light into their mouths you'll see two beams of red light come out of their pupils. Looks weird as hell. Found out accidently while checking to see how much of the inside of its mouth was black. It used to freak my ex out completely. The inside of their heads seem to be all mouth cavity. When you do the pen light trick they look like polynesian demon masks. Did I mention I recommend owning the females?
In one terrarium I have an african bullfrog, Frogzilla, one of the worlds few types of scarey frogs. Homeys got TEETH! Well, since you folks here are such sticklers for accuracy they are technically odontoids which differ by being actual extensions of his jaw bones. Totally non-mammalian arrangement as well.
When he was smaller I caught him and used a pencil in his jaws to examine his teeth. In the upper jaw there is a central spike, double edged like a dirk, flanked by two teeth that curve outward like scimitars that are also double edged. I personally think its to increase the shearing area without increasing the size of the teeth. Two "dirks" in the lower jaw fit between the three uppers. I had gotten curious after he bit a six inch goldfish in half at the middle and wondered how he did it.
When he closes his mouth it sounds just like scissors closing. I kid thee not. I feed him chicken wings occasionally and you can hear him break the bones when he bites down on them. Sounds like pencils breaking.
As he likes a terrestrial tank I give him a tank half full of potting soil kept really moist. Burrows down backwards and is happy as hell. Except when I forget to dampen it suffiently and he burrows down to the bottom of the tank looking for the moisture level.
Here's where it gets funny.
I forgot to water him once and as usual he burrowed down to the bottom of his tank. I know this because you can hear his backside rubbing against the bottom of his tank. Thats when I know to water him again. Sounds like when you rub your thumb hard on a damp window.
Well, across the room in another tank I have a spotted rapheal catfish. It seems the frog rubbing his backside against the tank bottom sounds just like a challenging male spotted rapheal, because he started making an identical noise every time the frog made noise and began to race furiously around his tank.
He would go berserk ever time the frog's butt would rub. When I noticed this it was so funny I dropped the cup of water I was going to water the frog with. I finally had to move Frogzilla into my bedroom just so the catfish could have some peace.
Well, thats my Saturday afternoon story.