Got my betta in May of last year as juvenile. He has been happy and healthy for almost a year. I regularly check and change the water. All has been good.
Last night I noticed for the first time temps almost in the 90's. Fish was fine. I unplugged the heater and adjusted the temp.. still kept triggering the heating element. I assumed the thermostat in the heater was shot, and continuously triggering the heating element.
Anyway.. I unplugged the heater last night and this morning the temp was around 73. Fish still seemed fine and vibrant.
I plugged back in the faulty heater to get the temps up.. and cycled it on and off by unplugging it. Temps cycled from high 70's through low 80's.. Throughout the day he seemed fine.. I bought a new 50w heater.. tested it in unconditioned water.. After testing (held a temp of 80 degrees perfectly) I dropped it in.. I'm sure it had some residual unconditioned water on.. but I assumed it was insignificant. Watched temps for a while.. locked at 80.. all good. Fish seemed fine.
About 2 hours after I put the new heater in, the fish is now on the bottom of the tank.. barely moving, white around the mouth and gills. He does swim around to go to the top for air and then comes back down again. I dropped a bit of food in his line of sight.. he darted for it.. but then came to rest again.
My question is.. is this likely a delayed reaction to the massive temp flux from the night before or possibly something else related to the new heater?
My old heater was a hydor 25w Theo, my new one is an Aqueon 50w. The new one might be considered slightly overkill for the size of the tank.. but not by much.
Any ideas? Does the shock usually pass? any guesses on something else? Should I have treated the new heater with something?
thanks so much!
5 gallon tank, filtered, cycled.
ammonia, nitrite, nitrate all good.