Are you only stocking one Sarasa in the tank? They are really more suitable for ponds. You can only have one in that size tank. Mine would also eat the shrimp. Goldfish really prefer a companion. How about several fancy goldfish?
Oh good - I see you found the goldfish forum ... I was just trying to figure out how to link it.
Yeah, I just read an article earlier today that said they will gobble down duckweed. I had thought about this post from yesterday.
it was SO funny.. I added these two little guys and a couple of handfuls of duckweed given to me by the pet shop at the same time. They would get up under one and suck the root and tiny leaves down like a spaghettI noodles
Alternately, what I have done is rescued the duckweed that was left and put it in a pretty bowl with some tank water, I'm going to let it grow there and then transfer it for them to eat/play with as it grows. You could try that too?
I would suggest a floating plant ring. It will keep the duckweed corralled, and then you can feed it as desired.