Flatworm eater for pico tank

[fishoholic]

My 2.5g tank has become over run with flatworms I had a barnacle blenny which I wonder if he was eating them because shortly after he died I noticed flatworms appearing. Thankfully they are just the plain ugly ones and haven't done any damage to the corals, they're just over taking the tank.

I tried adding a small scooter blenny to eat them, but he seemed depressed in such a small tank and wouldn't eat anything so I re-homed him in my big tank. Was thinking maybe I should add another barnacle blenny (however I can't seem to find one available) and see if it eats them or maybe try a geometric pygmy hawk. The only fish in the tank is a green clown goby and unfortunately he doesn't touch them.

The tank is to small to treat chemically (ie: flatworm exist) as that many flatworms dying all at once would crash the whole tank.