well it depends on the kind of fish you have. if it is a betta it will need a small bowl (very small)..don’t put it near window..if you need to put it far away.

you only need to feed it twice or once a day..if you need to do it twice..once in the morning..and once around 3ish..

have a light..nearly directed over the tank too.

How do you wash their bowl? If you use any cleaning solutions that might be your problem right there. Also, fish have tiny brains, they’ll eat untill they explode, so make sure you’re not over feeding them. And what type are they? There could be several special things that you need to do considering what type of fish they are. Do you regularly check the PH balance? Do you always use water conditioner when you do water changes? These are all small things that could add up. I hope you do well, and I hope you’re fish will be okay.

buy a tank for them that always keeps them clean… there may be some scum on the sides of the bowl that you can’t see.. i also had fish and died like 10 days later.. they say that you can over feed you fish very fast.. they say to take a tooth pick stick it in your mouth and quickly dab it in the feed container and stick it in the bowl… also buy it some toys to bight up the room…

maybe there is soap residue left in the tank from cleaning. Or, maybe you aren’t letting them adjust to the tank tempature before letting them out of the plastic bag. Sometimes the change in temp is too shocking for them and they die.

when you get a tank let a few cheap guppies die inside it so that it can get some bacteria started to grow it there, it creates a more natural environment for the fish instead of just plain water
and no water that comes from the tap if you do not get water from a well, that will kill them real fast

What kind of fish are they? Certain fish need certain types of bowls/ aquariums. If they are goldfish, they need to be given oxygen so you need a small aquarium. Make sure you aren’t giving them too much food. I have had a fish die from being overfed. Good luck and let me know how it goes!

Well, you should buy a small tank and get one of those oxygen bubbler thingys. They help put oxygen into the water and keep your fish alive. Trust me, this usually works. Good luck!