Male Betta fish tank issue

Question
One month ago I bought my son a beautiful aqua colored male betta. Within 5 days there was a layer of Slime on the gravel holding all the non eaten Tetramin pellets. the water was very foggy and smelled gross. I cleaned everything with bleach water and rinsed very well. When the air hit the slime it to to a gelatin like substance. I filled the tank again put in the spacial water conditioner one tiny piece of aquarium salt and put the disinfected air hose with disinfected soap stone back and put the fish back in. It has been 2 days and the same problem has accrued. What is going on with the fish or the tank. This time I thru out the gravel and all contents of the tank minus the soap stone which is being disinfected again. I use a miniature bottle cleaner to clean all the hoses and use rubbing alcohol after I have thoroughly rinsed everything. Nothing but the fish will be in there until I get more gravel. what could be causing this and is there anything more I can do. I want to save this beautiful fish.
thank you.
Ginnie

Answer
Hi Ginnie.  I'm afraid this question is going to be rather hard to address. There are many many things that have been done not quite right, so we will try to address each one.

1.  The "layer of slime" came because of your over feeding the fish.  If you are feeding pellets, the fish only needs 2 maybe 3 pellets at a feeding.  If he does not eat the pellets within 3 minutes or so, remove them, do not let them sit on the bottom, because they rot (as you have found out).
2. You should never use chemicals to clean your tank. No soap, no bleach, etc.  These chemicals can leave traces that can kill your fish.  Hot water, paper towels and a scrub brush/sponge made for fish tanks should suffice. I don't know what you mean by a "disinfected SOAP stone"??
3. It is good that you are using the water conditioner. Just be sure to follow the instructions.

I think the problem you are having is coming from over feeding.  You only need give the betta 2-3 pellets at a feeding as I said.  Remove anything he doesn't eat within 2-3 minutes. Make sure that the food is made especially for Bettas also.

Clean the tank out weekly, removing the stones and rinsing them very well with hot water, using a paper towel to clean the walls of the tank and the plants/ornaments.  Be sure that when you replace the water that it's about the same temperature as the water you took out so that you don't "shock" your fish's system.

Do not use any more cleaning chemicals on the tank as I said. This could potentially kill the fish, plus, they are not necessary.  Try this for a couple of weeks and see if you see a difference in the water.

Write me back if you need clarification on anything or if you have any more questions.  Good luck!!   ;o)