dropsy prevention? RIP Paco

I sent in this pic for POTM last week and he died this weekend; he was my office buddy:



I've had it happen before to a betta years ago, dropsy I believe. Over last week he began getting lethargic, then Friday his stomach was slightly swollen, and I knew it was a death sentence. Monday I found him dead, in rigor, with his fins extended out in full glory.

From what I've read, I can't find any ways to prevent it. Did I do something wrong?

Sorry for your loss.
Most commonly dropsy is caused by an internal bacterial infection. Poor water quality is the most common cause of the infection but not the only way to get it.

I don't know what the water change scheduled looked like at the office but that would be my prime suspect. If not a bacterial infection caused by water quality it is just a best guess sort of game.

Ah that could be it. There is no filter, just water changes, about 3-4 times a week about 25%. I really don't want the 2.5 gal tank to be overrun with equip; it's already small as it is and equipment is pretty chunky.

I am so sorry for your loss! :(