The pet store did just what they are there to do. Separate you from your money. It sounds like they did a great job of it too. Sorry to hear about your loss, and I understand your frustration.
In order to have a better experience the next time around, the first things you need to do are 1- Research. 2- Research, and 3- Research. Read the sticky threads at the top of this forum. They are there to help you.
It sounds like you're a new aquarist. I suggest reading the sticky threads in the general aquaria section. You need to have an understanding of the nitrogen cycle and how it works to keep fish alive for more than a few days.
Buying chemicals from a fish store is not the answer. It will only drain your wallet and frustrate you. The fish store will keep on telling you to purchase this and that, and your fish will keep on dying.
Understanding that an aquarium is a small ecosystem with symbiotic relationships between fish and microorganisms IS the answer, and believe me, there is A LOT to learn.
For the sake of your future fish and also your sanity, read up before you buy again. Everyone on this forum is here to help you, and many have been doing this for years and years.
Again, sorry to hear you had a bad first go of it, but make it a learning experience and things should get better. Welcome to MFK.
In order to have a better experience the next time around, the first things you need to do are 1- Research. 2- Research, and 3- Research. Read the sticky threads at the top of this forum. They are there to help you.
It sounds like you're a new aquarist. I suggest reading the sticky threads in the general aquaria section. You need to have an understanding of the nitrogen cycle and how it works to keep fish alive for more than a few days.
Buying chemicals from a fish store is not the answer. It will only drain your wallet and frustrate you. The fish store will keep on telling you to purchase this and that, and your fish will keep on dying.
Understanding that an aquarium is a small ecosystem with symbiotic relationships between fish and microorganisms IS the answer, and believe me, there is A LOT to learn.
For the sake of your future fish and also your sanity, read up before you buy again. Everyone on this forum is here to help you, and many have been doing this for years and years.
Again, sorry to hear you had a bad first go of it, but make it a learning experience and things should get better. Welcome to MFK.
so after all of that i took the dead fishes and i left that water for like 3 days cos i was lazy to clean it and started to appear snails everywhere. then i cleaned everything and i put new water and i used stress coat because i want to cycle the water this time first. i bought plants so i would like to know when i can put them in cos i think i can cycle the water with the plants in 
. and that is it maybe someone can give me an e mail so i can get better help or can explain me how to pm 
mm well now u think is ok leave them there so they can decompose? i just would leave them if it is OK to cycle the water with that. and also if the idea of keeping piranhas for a while in a 30 gallon tank is still a terrible idea i wont do it then 
.50