deffinately different, they will flip upside down and go rigid and twitch.. this happens with the eels in that tank as well. they last up to a minute w/out longterm negative effects i can see, they also occur every few hours up to minutes depending on the waters TDS.. a water change is needed or mortalities start. random fish will get it but the all do, one fish may be "tweeking" while another just stopped... i generally do a big water change the first fish i see... i ignored it once and woke up to 1/2 my tank dead... while every water test was fine ( i tested the water that night, and in the am) other then showing slight ammonia in the am, whoch would be expected the water was spot on. tank gets regular maintenece otherwise includeing water changes weekly.