Trying to find out what happened...

Hi,
I am so sorry your VT has passed on. If you could fill out the questionnaire below, we may be able to figure out what had gone wrong (if any) while under your care. Sometimes the bettas may have suffered negligence from the pet stores and already had some underlying issues before you got them home. But let's figure out from your end if things could have been prevented.
Good luck! Hope you have a better experience next time!

Housing
What size is your tank?
What temperature is your tank?
Does your tank have a filter?
Does your tank have an air stone or other type of aeration?
Is your tank heated?
What tank mates does your betta fish live with?

Food
What type of food do you feed your betta fish?
How often do you feed your betta fish?

Maintenance
How often do you perform a water change?
What percentage of the water do you change when you perform a water change?
What type of additives do you add to the water when you perform a water change?

Water Parameters:
Have you tested your water? If so, what are the following parameters?

Ammonia:
Nitrite:
Nitrate:
pH:
Hardness:
Alkalinity:

Symptoms and Treatment
How has your betta fish's appearance changed?
How has your betta fish's behavior changed?
When did you start noticing the symptoms?
Have you started treating your fish? If so, how?
Does your fish have any history of being ill?
How old is your fish (approximately)?

Housing
What size is your tank? 1 gallon
What temperature is your tank? 78-80 degrees
Does your tank have a filter? no
Does your tank have an air stone or other type of aeration? no
Is your tank heated? yes
What tank mates does your betta fish live with? he had no fish mates

Food
What type of food do you feed your betta fish? tetra betta floating mini pellets, and blood worms (but not often)
How often do you feed your betta fish? 2 times a day a 2-3 pellets in each feeding

Maintenance
How often do you perform a water change? every week
What percentage of the water do you change when you perform a water change? 50% water change on day 4, 100% water change every 7 days
What type of additives do you add to the water when you perform a water change? Betta safe water conditioner

Water Parameters:
Have you tested your water? If so, what are the following parameters? no

Ammonia:
Nitrite:
Nitrate:
pH:
Hardness:
Alkalinity:

Symptoms and Treatment
How has your betta fish's appearance changed? had a white spot under his stomach and had grown thinner the day that he died.
How has your betta fish's behavior changed? would not go after or flare at his own image on 2 day when he stopped eating. Activity started to go low, would not go after food.
When did you start noticing the symptoms? a day before death (room mate noticed)
Have you started treating your fish? If so, how? could not treat before death
Does your fish have any history of being ill? for as long as I had him no.
How old is your fish (approximately)? _________only had him for a week and 3 days before death_________

Sorry to hear about your loss

I am wanting to say the white belly isn't the cause, as fish tend to change on the underside from time to time- sometimes it's from a full belly, other times it could be a response to an illness.

It seems as if you had done proper care for him- great water changes, good tank and everything. Whatever had happened to him wasn't from anything you have caused- the only thing that does come to mind is something possibly getting into his tank via the open water- such as perfume or air freshener- so I would watch what you spray in the area to make sure it doesn't get in there.

A lot of times we will get fish and shortly after bringing them home they pass away suddenly. I tend to call it "New Fish Syndrome".. as we can't tell where they came from, how they were bred, etc. It's always a risk bringing one home, as we fall for them so easily and then something such as this happens.

I wish there was a simple answer, and that he had given you a little more time to help him. But I don't think anyone can answer what had happened, since a white/silver belly isn't definitive of an illness, but either a symptom of any number of internal problems, or from a rounded full tummy and even stress.

Again, my sympathies on your loss.. don't give up, you had done right by him.