Why are my fish constantly swimming at the top?

If they are new fish in a new tank then the first thing you did wrong was putting fish in new water.. You should always leave a tank running without fish for 2 weeks. Water has a natural cycle that can kill fish. Go buy some water testers and you will very quickly find the problem. If you don’t your fish will die very soon. I would also look at feeding them once every day or two. You are far better off underfeeding then over feeding. Over feeding will very quickly distroy your water quality and they will start doing what you described.

I dont know what type of fish or how big your tank is but I would start doing 20% water changes for a few days until the quality gets better. Also make sure you are using the right product to make tap water safe and follow the instructions perfectly.

their probly trying to get oxygen if you dont have a pump or filter then theyll probly die soon or else their just stressed from the move into the tank and should be fine soon but if their having a hard time swimming and are falling on their sides and swimming weird then they probly just have air bublles if its a beta fish then drop half a pea in the tank for them to eat it pushes the air bubles out ^_^