Miles with Glass Fish Originally uploaded by Unkoine. Q: TI wrote, What is the best substrate to use in a Betta tank? A: There is more than one answer to your question because, truthfully, it depends. There are a variety of substrates out there ranging from fine sand to gravel to rocks or marbles. Choosing which one is right depends a little bit on the type of set up you … [Read more...] about Choosing a Substrate for a Betta Tank