Sick Betta! Help :(

Question
I love my little betta Nappy and I was trying to be a good mother and get him a little house to sleep in so he wouldn't be bothered by the lights, and I think I poisoned him. I know I should have gotten him a fish house, but all the ones I found weren't the right size for him. So I found something that looked like stone (marble) so I thought it would be ok to put in water, I washed it, put it in his cage on Sunday. Last night (Monday) he was lethargic and this morning(Tuesday) he wasn't moving or eating. I immediately took out the little house and it smelled like chemicals, so it was obviously making him sick. I put him in a new bowl with completely fresh water, but he looks bad. I didn't think he would make it through the day, but he's still alive. He stays pretty still, looks pale, won't eat, and tries to stay near the top but gets too tired or something and just sits at the bottom. He was a very healthy fish before. Is there anything I can do for him? I don't want to see him suffer, but I also hope he can pull through this. I'm just scared that fish are so little that when they get sick thats sort of it for them :(
Thanks so much for your help

Answer
Eva,

Sounds like he has been poisoned, fish absorb chemicals through the skin and it takes very little to to terminal damage. There really isn't anything you can do to save him, once its in the bloodstream it cant be filtered out.  I would chalk this up to a learning experience and in the future stay with items made specifically for aquariums.