my brother just cleaned the tank yyesterday and i wake up this morning and one is dead and another one is dying water temp 77 ph 7.2 alkalinity between 80 120 nitrite 0 nitritesbtween 20 and 40
What did he clean it with? Sounds like he didn't use dechlor or added way too hot/cold water... Do they appear to be gasping? Another 60% wc with grated water and matched temp! Prime will help.
Not sure in twelve hours that less to no bb will kill it, my filter recently shut off for 36 hours, no bio or mechanical filtration, new substrate, new setup, turned it back on, tested water every 24 hours and it never changed, no ammonia detected. To this date I'm still very shocked, I expected Atleast a mini cycle!
Sounds more like its something to do with the wc, maybe your Bro overdosed the prime on accident. I still strongly suggest a wc ASAP!