This is a super fun hobby, and it may turn out that you very much enjoy it, but it's a lot less fun when it consists of cranking in fish after fish and watching them suffer or starve. That outcome is avoided by researching procedures and animals in advance. Many people start without really knowing what they are getting into, nothing to be ashamed of there. It's how you deal moving forward that says something about you. Personally, I'd take a step back and start from the beginning. Just run it with the snails and hermits and read stickies for a few weeks. We'll help with anything that doesn't make sense.
You seem to be asking for ways you can care for the mandarin in your tank as is? No. Take it back. Read up on them, learn about their food and needs, and then when you've really got your head around it, buy another.
There are so many people here that are very knowledgable and happy to help. I'm still a noob, but just speaking for myself I'm not really comfortable helping people figure out ways to take shortcuts on stuff like tank size and diet. A more extreme analogy would be if you bought a greyhound, brought it home to a tiny apartment with once weekly feedings, and started asking advice on what brand of kibble would make the best of the situation (and making comments about how the dog was in a crate at the store so it can prolly live in one 24/7). I know it's just a fish, but it's still a pet that depends on you