I have one that is pretty large. It's only been in my tank for 3 months. But Ive been reading alot on Goni's and I hope I can make it last. I have it in a perfect area for flow. Its extended all day long, and at night I make sure there is nothing b/w the tentacles when its closed up partially.
I spot feed it a mix of live phyto, oyster eggs, and crushed cyclopeeze twice a week. And my tank gets fed the same maybe once a week. There are also lots of small pods in my tank that im sure the goni eats.. (obviouslly the really small almost invisible pods.
So far it has a definately feeding response when I feed it, and it's been growing at a fast rate.