About 4". I’m running a filter and doing water changes. I plan to move one into another 10 this weekend if I can find a big enough net. 
Don’t suppose you’re in Arkansas and want one?
Well, I would take one but I’m not even in the US of A.
If you can move one of them to a different tank, that will help a little. It’s pretty normal for them to be a bit skitish - my guy still whips around like a psycho if I move past the tank too quickly.
However, if you can arrange a couple of rocks or plants that they can hide under/behind they should be just fine.
They’ve got flower pots. It’s that THUNK when they smack into the side of the tank that is unnerving.
Sometimes it’s not so much the size of the tank you need to worry about as it is the size of the opening at the top of the tank. Growing up, I had a 50 gallon freshwater hexagonal acrylic tank that was about 24" x 24" x 24" - which seemed like plenty of room for a 3" pleco, a bad-tempered cichlid, and an assortment of other smaller fish. Unfortunately the opening in the top of the tank was rather like a mail slot in your front door.
Tragedy ensued when the pleco died after having grown to about 14" in length. It should have been transplanted into another tank, but frankly we were all too scared of it and the spines on the ends of its fins to dare. By then the other fish were scared of it too, so who could blame us? Anyhow, the equation of death went like this: 14" pleco with spiny fins outspread and locked in grim rigor mortis + 4" x 8" aperture in the top of the tank = emergency piscine surgery, as in “cut through your foot, not through the shackle.” Yuck.
Beyond this grisly story I have no further advice, save that which has already been offered. I would definitely pull the filter and check it for nasty bits. Although it’s in my experience rare for an entire fish to get sucked up in there (unless it’s a dwarf siren*), you may very well find bite-sized portions trapped in odd corners if the lil fella did get eaten and wasn’t completely consumed.
- That’s another story in and of itself. Thinking about it, I have enough stories that our aquarium was really a Series of Unfortunate Fish Events. Maybe we need a thread called “Gruesome Aquarium Stories.”
Why didn’t you just remove the capper?
Another sign you can look for is a cloudyness to the tank.
If certain bacteria have a source of food (decaying fish or extra fish food), they will reproduce and fill the tank with a white cloudyness.
But if you’re ammonia is doing fine and the water is clear, I would say the fish eitehr jumped out or got eaten.
That was the thing. There was no capper. I don’t know how old the tank was, or where it came from - I’m guessing it was homemade or converted to aquarium purposes from some unimaginable engine of destruction found in a super villain’s lair, although it’s possible it was a model from the Early Soviet Acrylic Age - but it was a solid mass of acrylic with a slot cut in the top for the light and a hole drilled near the back of the top for the filter tube (the filter itself just sort of sat on top of the tank). To access the interior of the tank, you lifted up the light and added food or whatever other necessities were required. My mother could just barely get her arm and a suction tube down through the slot for cleaning purposes.
You could in theory crack the top of the tank away from the seam, but it was not meant to come away from there any more than the hexagonal sides were designed to separate. I think you’d need the jaws of life or a jigsaw to manage it, and it woudn’t be an operation you could undertake while the fish were boggling around inside.
Probably the moral here is “don’t assume it will work as a fishtank, just because it looks like one.” Or maybe, “there are fishtanks, and then there are fishtanks.”
:eek:
Wow. That must have been a huge pain in the ass. Like HUGE.