Brine shrimp are commonly referred to as fish 'potato chips' due to the amount of nutrition they contain (they have almost none). If you can gut load them with Selcon or some similar additive, that might help.
I have heard of some folks being successful with a mandarin in a 55 gallon tank, a 30 is rather doubtful unless you have a huge fuge for growing pods
. You could set up a small tank for raising pods
and feed the main tank from there. The number of people who are able to get a mandarin to eat prepared food is rather small. Usually the fish starves to death over a period of months due to the lack of food in a small tank.
This is the second time I've read a post from you declining to take advice from people with more experience because you don't think they are correct, or because you don't feel like it. That is usually a precursor of a tank disaster.
I wish you good luck with your tank.