Nothingness: what kind (size) of tank/bowl are they in? Bettas actually live in mud puddles in asia (i think Asia) and so they can take not having the water changed that much.My sister in law once left hers go for so long (I don't recommend this,lol) that you could not see in the bowl!!! God Bless the little guy cuz he was fine and dandy! You might check with the pet store too,they can help.