Crusty stuff around tank

Question
I have a 10 gallon tank in my Kindergarten classroom (and have had it for approximately 6 years) with three goldfish.  Over the past couple of months, a buildup of "white crusty stuff" has begun around the filter, top, and waterline (if it drops).  What is it and how do I keep it from coming back after I scrape it off?  Thanks!

Answer
Hi Julie;

It is simply mineral deposits from water evaporation. There really isn't anything you can do in the aquarium to change that. It's just a natural component of tap water. Some are worse than others. If you add salt to your goldfish tank it can cause deposits too.

Since it only started in the last couple of months, maybe the school changed water systems or there is a water softener that isn't working properly? Perhaps someone disconnected or turned off the school water softener?

At Your Service;
Chris Robbins