what should i put in my 3 gal. i will also say that it is a "tube". it is ABOUT 16in tall and the circle is ABOUT 8-12 in across. it will have fake plants and maybe some little deco. i have yellow medium gravel. can i use that or buy new stuff. if buy new then what? what kinds of filter? do i need heat? and of course, what shrimp and how many??