Tomoko, I'm thinking about setting up my mom's old octagone tank for seahorses. Do you think seahorses and Mandarin's would be okay to live together. I would imagine it could be okay, but there might be somethig I don't know. Also, I'm interested in reading about supplementation with a glass jar. I will serach for this. I had one, but it died probably from starvation. I've been afraid to buy another one. Thanks!!!