Betta Fish / Killed 2 scared to get more

Question
My son had 2 betta fish (one boy, one girl they are seperated) we got them in January and I killed them accidently yesterday.  We have a 5 gal tank that has a small filter, we have rocks on the bottom and 3 plastic plants.  I was doing a partial water clean weekly and stupidly attempted at full water clean yesterday I used soap and water to clean the tank and rinsed it thoroughly rinsed all rocks in hot water only, and rinsed the plastic plants in hot water only.  I put everything back in the tank, added warm water and water treatment drops and dropped the fish back in within an hour prob less both fish were dead.  I know I messed up using the soap and water but if I remove everything add new rocks and plants and let the water be room temp in the tank we have will a new fish be safe?

Answer
Hello,
I'm sorry this has happened, and that you have lost your fish.
You must rinse, and rinse, and rinse to make sure there is no residue of soap left in your tank.  Change all filter material, and rinse that too, over, and over again.  Buy new rocks, and new plants.  Then add water, and add A good water conditioner such as Stress Coat, or AquaSafe.  Always make sure when adding a Betta to the tank that his water is exactly the same temperature as the water he is in.  
I also would like to mention that one Betta needs a 5 gallon tank all to himself to be happy, and healthy.  He should not see another Betta, male or female close to him as this causes stress, and sickness.  In his habitat, the Betta's water may be shallow, but they have lots of room to swim.  He is a tropical fish, and he should be in 80 degree water which does not fluctuate, and his water should be changed every week.  If you do raise his temperature, if you buy another Betta, do this very very slowly.  One degree every second day, as raising the temperature too quickly could cause death.
Adding one teaspoon of diluted aquarium salt to his tank is also very good for him.
Vary his meals as much as possible.  Betta Pellets one day, Betta Flakes the next, Daphnia the next, and Bloodworms the next.  He should fast one day a week, and on that day he should have a cooked frozen pea.  Remove the outer layer, and cut it into small pieces.  Feed this to your Betta, one tiny piece at a time, making sure that they don't fall to the bottom of the tank.  This helps clean out his system, and prevents Swim Bladder Disease, which is caused by poor diet, and leads to constipation.
The Betta is one of the most mistreated fish on the Market.  Too many are kept in small containers, one gallon vases, and so on.  This is cruelty, and there are no laws to protect fish.  Vendors send you home with a Betta telling you that small containers are perfect, and bloodworms is all he needs.  Soon the fish get sick, money is spent to cure them, and eventually the fish dies.  This hurts the person who has grown so attached to them.  They are intelligent little beings, and should be treated right.
I just thought I would mention this to you, as I breed them, and love them.  A Betta when bought young will live up to 8 years if treated right.  Of course we do not know their age when we buy them a the pet store.
Hope this helps
Lynda