Possible reasons my fish died?

Well... It could be full of nitrates and ammonia. I've had a Red Wag Platy, 2x Neon Tetra, and a Guppy die because of my stupidity. I didn't wait for the bacteria to build up. My Betta recently died of cotton mouth and he had the same "seizure" like motions. Maybe a pathogen damaging his brain.

Only change 20-25% of the water at one time. Let the fresh water sit out in a bucket, pitcher or whatever overnight so it is room temperature when you need it.

To properly keep a Betta, you need at least a 5 gallon tank with hood, heater, and gentle filter.

You never remove the fish to clean the tank. You use a gravel vacuum to clean the gravel while siphoning out the old water. The fish will move!

Before jumping head-long into getting a new fish, take some time to learn about tank maintenance and Betta care. With some research, your next fish might live his full life-span of 5+ years.

When it is a fish's "time" he normally won't act like he is having a seizure! Usually, you just look in his tank at some point and find he has passed.

Sorry for your loss.

I can't say the water change is exactly what killed him or not it could be several things.

But I can say that it is not good to change all the water at once in ANY tank.

You should have a heater for your betta with a tank at least 5gal and a nice small filter that doesn't stir up the water a lot.

Every week you can do water changes of about 25% of the water and that should keep the water clean. When doing water changes you add water that is about the same temperature of the water. Not too cold or hot! This could shock your fish and definitely kill them (which might be what happened).

Once you have everything set up, decorations, filter, heater, etc. for at least a week running then you can buy your fish and acclimate him to your tank water temperature which should be 76-78 degrees Fahrenheit and then put him in after about 10-15min.

If you have any questions on setting up your tank I would recommend look up videos on YouTube. Please do not buy another fish without doing a little research on keeping them. Once you learn a little bit I know that you will an excellent fish keeper. Good luck to you.

Touching up on what the primary poster said. If it is a new tank, it desires to move by way of the Ammonia cycle. This more often than not takes a couple weeks. Whilst you add fish to a tank, the fish offers off ammonia. It is very detrimental to fish. After the ammonia, i suppose it is nitrites that spike, and ultimately the nitrates which aid hold the opposite 2 in investigate. All tanks ought to go by means of this. To move via this cycle, you should get some hardy fish, equivalent to danios or guppies or some thing your decide upon. It isn't recommened to start with greater than 25% percent of your capacity nor must you ever add greater than 25% of that potential directly. It will harm all of your fish. If that cycle isnt the case, then you definitely will have to specify exactly what form of fish you have, the specified measurement, and many others. Distinct fish cannot reside collectively. Additionally, there are directions as to how many fish you contain in a tank. A basic rule is 1 inch of fish for every 1 gallon. But, there are exceptions.

Maybe because the water was a bit colder. Your betta must have the same water temp as he had when you took him out to clean the tank. Changing the water temp can make a fish really stress untill they can't take it and die. Btw betta fish can live more then a year with good care like ( a tank 2.5 or bigger/ filter/ heater/ plants real or fake / gravel.

Certainly could be temperature shock. Not sure what your tap water temp is, but if it's less than about 70F it's going to stress a betta, down under 60F it will probably be fatal.

Ideally you want a decent size tank that can be filtered and heated. Then you never remove the fish from the tank, simply vacuum, wipe down the algae, and change part of the water. This is MUCH less stressful for the fish.

Ian

If you get a gravel vaccuum while you are at the fish store then you won't have to stress your fish out by removing him from the tank. If your tank is too small for a gravel vaccuum then its too small to keep a fish in. Betta fish should live 5-6 years.

bettas come from hot shallow water in the wild, so it's entirely possible that the water being colder is what did it.