My students (elementary aged) read a passage about terrariums this year. Excited they did some research and we converted a 75 gallon fish tank into a terrarium. Things have gone well for the past 6 months, but since spring we've had some odd growth.
In the bottom of the soil some round, white spheres have shown up (a bit of a yellow tinge). They have invaded the areas under the charcoal. The plants started out small, and have grown nicely. All plants came from a reputable nursery that specializes in indoor plants and fairy gardens.
We used cleaned pebbles, and potting soil from a local large nursery. So far nothing has grown on the plants. We water once a week, and keep one side of terrarium open. the only odd experience came from a student who thought to add grass seed from a science experiment. You can see the little wisps of grass by the moss.
Any idea what the growth is? How to combat it?