how to build a terrarium? it's for a school project
hello! we are grade 12 students from the philippines. our teacher assigned us to make a terrarium as a group for our final project in our earth and life science subject so we can graduate high school. it is one of our major curriculum requirements. i am currently gathering rocks for our drainage layer. i read on google that we should test the rocks one by one with a drop of vinegar to see if they are limestone, which helps avoid rotting in the ecosystem. i am searching online, but i also want to get tips from people who have experience building terrariums. we are not allowed to open the jar once we close it, so we are struggling a bit with this part.
what kind of living organisms should we put inside? something that can sustain itself in the ecosystem we built? we are students, so we can't buy anything, please give us options we can find ourselves.
is it okay if we get rocks from the river? we live near a river, so we think gathering rocks there would be a great idea.
do we need to sterilize the rocks once we obtain them, or do we need to wait until we are told to assemble our jar?
what kind of soil should we put in there?
other tips would be appreciated. thank you!