Please help me,I am new to this fish aquarium keeping stuff. I have a 35 gallon tank, with fresh water fish, I had guppy's, zebra, tiger barb or what looks like,and molly lier tail {all non aggressive } bought from Petco. I also had a algae eater {which was 6" long } all die.I have had these fish for at least 6 months.I have added water like I have before which had chlorine remover added, according to the directions. The ph level to the safe color. The same tropical fish food.I've changed nothing. The pump for the bubbler went out.could the fish die from stress? What can I do to be a better fish owner? Is it that I have to stick to one kind of fish? I only had non aggressive. Thanks for your help.

Do you have any fish now?
If so, we can work on trying to figure out what went wrong and if there is anything happening inside the aquarium that may be causing death to fish.

If not, are you looking to start over? I can help you out there as well.

If you have a filter on your aquarium that created any amount of bubbles
As the water flowed back into the tank, then they weren't stressed due to lack of oxygen.
However, if they were not getting enough oxygen, that could pose a problem.
You don't have to stick to one fish when you are keeping a non aggressive community aquarium. Just be on the look out for the fin nippers like tiger barbs and that they are not nipping the fins of the other fish.

Also, sometimes fish have illness that are not obvious ones.
They could have just been sick...

Waiting on you.