First time in the forum folks, please be kind. I've had tropical fish for many years and believe I know what I'm (mostly) doing but haven't had an active tank for two years. We got our first betta last Friday (end-of-school gift for the kids) and all seemed to be going very well up through this morning; by dinner today he was dead. I want to try to identify the most likely cause of death before introducing a new betta because I don't want to repeat my mistake. Stock questions/answers below, but the narrative history may be relevant:
New tank, new gravel, new plant (Java fern), new betta, new tank decoration (ceramic log), new heater, new filter all purchased last Friday. Loaded tank with 2.5 gallons tap water + conditioner, rinsed gravel, rinsed decoration, rinsed plant, rinsed heater, allowed entire system to acclimate for 24 hours while betta hung out in his Petsmart container (ambient temp ~75-80F).
Introduced betta to his new home Saturday night, first by floating his container in the tank for 10 minutes, then mixed his water 50/50 with the tank water for 10 minutes, then let him loose. He explored the tank well, looked active and healthy.
Fed small pinch (~10 grains) Aqueon betta food 2x daily. He squeezed himself between the filter and tank wall at the surface frequently, starting Sunday, and just sat there. It freaked me out at first because he was so still but I believe he was just napping. Fins, gills, body all looked good and healthy.
Heater took 1+ days to get the tank noticeably above ambient. He seemed to be fine all week, moving about, feeding nicely, hanging out in his plant and log, all's well. This morning I saw he was napping in his log before work. My wife said he looked fine but didn't eat breakfast, did not dart after his food, and went back into the log. When I checked on him after dinner he was belly up at the surface, eyes cloudy, stomach slightly swollen but not oddly so, fins essentially disintegrated (not sure how else to describe it) and very very dead.
At this point the tank seemed very warm so I got an accurate thermometer...93F. The heater, allegedly, isn't supposed to be on with the water above 80F but I pulled the heater and it was toasty and clearly pumping out heat. Ambient was 75F, although the tank is beside a window with an A/C unit so it's locally a little cooler than that.
My initial feeling it was a simple, stupid, heater error. This I can fix. However, I don't want to overlook something else and subject the next betta to the same fate.
-Disease? Petsmart bettas have a spotty record but we selected this guy precisely because he looked healthy and seemed to be doing fine all week so I'm not sure that's it.
-Constipation/overfeed? Possibly...having done more research, I think we were overfeeding him but that doesn't seem consistent with the extremely rapid decline today.
-Water quality? Will check this tomorrow...the tank is too new to have established a good cycle but he's the only fish in a 2.5 gal tank so I'll be surprised if it overshot into lethal toxicity that quickly.
Basically, am I right to think this was just heat mis-management and I just need to give a new betta a good home in 75-80F water? Should I sterilize the tank and start fresh just in case?
My oldest son does not take the death of pets well; this will be an important learning experience for him but I don't want bettas dying in a week to become a habit. Any and all advice most welcome.
What size is your tank? 2.5 gal
What temperature is your tank? 93F (yes, this is too high)
Does your tank have a filter? Yes, Aqueon Mini-bow (charcoal/sponge)
Does your tank have an air stone or other type of aeration? No
Is your tank heated? Yes, Aqueon 10W
What tank mates does your betta fish live with? None
What type of food do you feed your betta fish? Aqueon betta pellets
How often do you feed your betta fish? 2x daily
How often do you perform a water change? Hadn't happened yet, tank was a week old, was planning weekly
What percentage of the water do you change when you perform a water change? N/A, planning 25%
What type of additives do you add to the water when you perform a water change? First load had Aqueon water conditioner per instructions + 24 hour break-in
Have you tested your water? If so, what are the following parameters?
N/A - hadn't done a check yet
Symptoms and Treatment
How has your betta fish's appearance changed? No change until immediately before death. After death, cloudy eyes, slightly distended stomach, fins almost totally gone (they were in good condition this morning)
How has your betta fish's behavior changed? Stopped eating this morning
When did you start noticing the symptoms? This morning, about 12 hours before death - went from fine to dead very quickly
Have you started treating your fish? If so, how? N/A
Does your fish have any history of being ill? No
How old is your fish (approximately)? 1 week from Petsmart, unknown prior