well, clearly the fish i introduced to the tank yesterday must have had something wrong with them. one died while hiding in a seashell, the other stuck to the filter. that will teach me to use a quarantine tank. ugh. i feel so rotten! anyway...i'm afraid they may have introduced something to my tank. sigh. i woke up this morning to find my two other fish alive as always, but one of my zebra danios has pale swollen lips, and his mouth is fixed in an open position, not opening and closing the way a fish's mouth usually does in sync with breathing. his mouth is normally white regardless because of the striped pattern on his face - the pale colour just happens to run across his mouth - but this is very different. they aren't hugely swollen, but enough that it's noticeable close up. he isn't swimming much. just hovering in one place. note...water parameters are as always: ammonia 0.25 nitrite 0 nitrate 5-10 if you recall my previous posts, my parameters have ALWAYS been these values, despite being set up for two months, so we've been thinking perhaps my api master kit is giving me a false 0.25 reading. totally angry at myself for screwing this up!