Can you tell us more about the system? It is hard to make any statements with what is being said.
The unfortunate part here is that usually by the time we notice mandarins not doing well it is already too late. Take what seaweed said about them and understand how these fish are built to survive. They swim around and eat pods, some have even stated 1 every second, due to how their digestive system is built.
I kept one when I first got into the hobby. I was arrogant and thought that I could do it. It cost me a ton of money in pods that I dumped into the tank on a monthly basis. When I found him eating mysis, I stopped buying pods and it starved to death.
These beautiful fish simply belong in the ocean.
