The green Goni's are very hard to keep alive they need a lot of food where in a reef we cant provide, the most time i kept one alive is about a month at the most, but if everything in ur tank ur water parameters are normal maybe is just adjusting to ur tank, what are ur water parameter? on the other hand if u want a easier Goni the Red Goni is a better choice, i kept one for at least a year but i put it too close to my GSP and my GSP kill it.