I couldn't figure out exactly what happened here. This Dwarf Neon Rainbowfish was swimming around with her mouth wide open. No clamped fins, or other problematic signs. She was swimming around fine.
Now she's back to normal (around 10 minutes later).
My theory is that she swallowed a pellet that I put in for the Corys and it was lodged in her throat. The water dissolved it in a few minutes time and she was fine.
I have a 40 gallon 'breeder' with live plants, 7 Dwarf Neon Rainbows and 4 Gold Line Corys (Aeneus). Temp is 76F, and all chemistry is ideal except for nitrites, which is at 3 (my tank did not cycle before I put the fish in 2 weeks ago (:
To deal with the nitrites I am using Prime and Stability, along with every-other-day 25% water changes.
Any ideas what may be wrong with this fish? I lost one Rainbow last week. I assumed it was due to the terrible chemistry, but maybe I have something else going on.
For what its worth, my fish is fine now.
I really think she at something too big to go down her throat until is softened up.
(Just in case this helps someone else to NOT worry to death.)
My danio has its mouth stuck open and it looks similar to the picture, how long did your fish stay like that before it was fine?
No more than 15 minutes. The pellet must have dissolved and allowed her to swallow it.