Hi Brad,
Two options for the mandarin.
Slurper gun or the Philippine method of small harpoon. You could modify a gravel vac and siphon mandarin into it then cover the end. Just remove the siphon hose and stick your finger over where the hose attaches. Move the open end within a few inches of Mandarin and remove your finger from gravel vacuum hose barb. The suction should get the mandarin up into the vac.
You could catch the Mandarin like they do in the Philippines. Attach a needle to a stick and harpoon it through the top fin.
Cheers,
Tim
ps Thats why Mandarins are not cyanide caught... too east to get them with a harpoon or slurper.