It really depends on your idea of aggressive......eels, lions, etc need a lot of LR to be happy.
Here's a Photo of one of our 125 gal. tanks.
2 Juvenile volitan lions
1 dwarf fuzzy lion
2 scorpionfish
1 Maroon clown
1 Immaculatus puffer
1 Atlantic needlefish
1 Gulf toadfish.
Several curlyque and hermitcrab anemones.