# How to expand the box and randomly add water molecules?

**URL:** <https://gromacs.bioexcel.eu/t/how-to-expand-the-box-and-randomly-add-water-molecules/8009>\
**Category:** User discussions\
**Tags:** simulation-setup\
**Created:** [January 9, 2024, 10:10am UTC](https://gromacs.bioexcel.eu/t/how-to-expand-the-box-and-randomly-add-water-molecules/8009 "2024-01-09T10:10:54Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![keinerfan](https://avatars.discourse-cdn.com/v4/letter/k/e495f1/32.png) [@keinerfan](https://gromacs.bioexcel.eu/u/keinerfan)\
**Post date:** [January 9, 2024, 10:10am UTC](https://gromacs.bioexcel.eu/t/how-to-expand-the-box-and-randomly-add-water-molecules/8009/1 "2024-01-09T10:10:54Z")

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GROMACS version:  
GROMACS modification: Yes/No  
Here post your question  
Hello how can i expand my system and add water molecules to the expanded side? i dont know how to use insert-molecules command?, and also can anyone help me how obtain spc216 pdb or gro file ( the one that gromacs uses) so i can use it to add them with gromacs insert - molecules?