Yes, what a silly topic, right? But I believe I just watched one of my bettas fart.
I know land animals do it, but I never considered it among fish, until I saw 4 bubbles consecutively come from one of my larger bettas anus. If I didn't know any better, I'd have thought that one of the other bettas curiously went "sniffing" to see what it was following the trail the bubble made to the top.
Some fish observers claim they see a telltale bubble or two escape from the stern of a fish after it has gulped air at the surface (I have heard this said of tarpon). But again, this is not strictly a product of digestion.
Also in the article
Carbon dioxide is typically eliminated via gas transport to the gills; methane has to escape some other way. However, actual sightings of farting fish are rare--and let's face it, underwater this isn't a phenomenon that could be easily concealed. Some experts say digestive gases are consolidated somehow with the fish's feces, which are packed into a gelatinous tube and then expelled.
Maybe it was a fluke. I often see my fish expel air back through their gills, however this one definitely came from the anus.
Whatever the case may be, I think the fish might have gulped air when eating a flake, and went down low enough for a long enough period of time that the air worked its way down the other end, hence me seeing it where I did.
So, I'm not sure if you guys pay much attention to many of my other threads. But my fish have come down with collomanus cotti, a terrible parasitic worm.
The betta that I witnessed fart however long ago I wrote this thread was the first one to exhibit the protruding worms from its anus.
I began to notice the "farts" coming from some of the other fish as well, more recently, as I've become a little more accustomed to the different fish bing infected.
So now that I'm noticing all this, I've come to the conclusion that my bettas never were farting. The bubbles were warning signs. THey were the worms expelling air.
Kind of sad, but interesting by contrast - sort of scientific method, of observation. It gives me inspiration for this hurdle, even if all the fish end up dying, to make something better of it, and chronicle this as an actual article for a couple fish keeping magazines and web sites.