well I only had one fry survive so far

it is 3 weeks old now. I really want him to live he was my biggest most healthy one the whole time and the only one that ate well. I think maybe the others maybe have been in poor health at hatch it was my pair's first spawn and a lot seems to have twisty tails an stuff and I didn't many eggs anyways.
What should I do to improve his chances? This week is my first week start removing some debris from the tank floor. I am going to start aging some water to do a water change too soon.