YOU SAID:

never have i ever seen a big fat aquarium that walks down the road

INTO JAPANESE

道を歩いている大きな太った水族館を見たことがない

BACK INTO ENGLISH

I've never seen a big fat aquarium walking down the road

INTO JAPANESE

大きな太った水族館が道を歩いているのを見たことがありません

BACK INTO ENGLISH

I've never seen a big fat aquarium walking down the road