i agree with paul, except with the "it'll be okay bit.
if we have axolotls surely we must do our utmost to let them thrive and prosper, we need to stop axies from dieing, not using them as a lesson.
Stephen-i know you have been getting quite alot of stick recently, but take it on the chin. all we are trying to do is help you and your axies out. if any of them seemed rude, im sure we will apologise.
i would like to ask how sand "makes the filters stop working". the only way i can see this happening is if the filter is laying on the sand, in which case that is inevitable.
however, sand is the best, its PH neutral, so no problems there, and its by far the easiest substrate to clean. any excess food and you can just either syphon off or net it.
sorry to keep repeating what was said, but stephen, for the good of your axolotls, do the right thing, if you can, and get your parents to allow you to change to sand. show them my post,and tell them the people who are giving you this info have alot of experience, and ultimitely it is for the good of the axolotl.