mplspug, that is how fish act when there is too much ammonia in the water. It is highly toxic. It affects their O2 uptake. Bullheads are tough too, other fish would die much faster.
The bacteria that grow in filter media remove NH3 and keep your bait alive. Carbon and stuff works for a while but you need to keep replacing it. The fiber bag the carbon sits in is the real workhorse. It takes about two weeks for the bacteria to multiply and be fully affective at converting NH3 to NH4 which is much less harmful to fish.
You can make really simple filters. A simple one would be pumping water onto the top of a bucket full of lava rocks or furnace filter floss and letting the water trickle through that media and back into the tank. It adds O2 to the water also. I think an ice cream bucket would be fine for 20-50 gallons but the bigger the filter the more you can overcrowd the tank.
The hang on aquarium filters work fine but I don’t think they would fit on something with wide sides like a stock tank without some trimming. They work fine and are pretty cheap otherwise.
If you don’t have any filter you need to keep a low fish load or they will go belly up.
Bait is important, especially when gas is $3! Keep that bait alive!