..aka aggression levels.
The old freshwater division into 'community' vs 'aggressive' is not that applicable.
Carnivore, however, still reads 'carnivore,' and if a fish is prone to eat other fish, he will eat any fish that fits in his mouth. He's not aggressive---just hungry.
In general---take the size recommendations seriously and, honestly, add about 10% for safety. It's not saying the individual fish has to have, say 100 gallons all to himself, but that within a hundred gallons, this fish can move about, have a territory (if that applies) and his neighbors can move away from his territorial demand fast enough and far enough that no fin gets nipped.
You can also help define territory: place a distinctive vertical rock...you may find that the tank boss fish sort of hovers there. Fish, like humans, seem to value landmarks. And if you saw a shark pop up in view, you'd probably also want to see a distinctive marker guiding you rapidly and accurately to the no-shark-fits-here area, where you have a den. So your rockwork can help define areas of your tank. Some fish like to wander around. Others are the sedentary territory-holders. The wanderers are some reassurance to the others that there's no shark in sight: we call them 'dither fish', or fish in motion, up in midwater, which makes the other fish braver.
How many fish can you have in a tank of a given size? There's no single answer. Think of it as a Rubik's Cube of a space, in which so long as everybody can slide and move and grow in size, and the territorial curmudgeons can continue to chase the kids off the lawn without hurting anybody, you've got a good setup.
The old freshwater division into 'community' vs 'aggressive' is not that applicable.
Carnivore, however, still reads 'carnivore,' and if a fish is prone to eat other fish, he will eat any fish that fits in his mouth. He's not aggressive---just hungry.
In general---take the size recommendations seriously and, honestly, add about 10% for safety. It's not saying the individual fish has to have, say 100 gallons all to himself, but that within a hundred gallons, this fish can move about, have a territory (if that applies) and his neighbors can move away from his territorial demand fast enough and far enough that no fin gets nipped.
You can also help define territory: place a distinctive vertical rock...you may find that the tank boss fish sort of hovers there. Fish, like humans, seem to value landmarks. And if you saw a shark pop up in view, you'd probably also want to see a distinctive marker guiding you rapidly and accurately to the no-shark-fits-here area, where you have a den. So your rockwork can help define areas of your tank. Some fish like to wander around. Others are the sedentary territory-holders. The wanderers are some reassurance to the others that there's no shark in sight: we call them 'dither fish', or fish in motion, up in midwater, which makes the other fish braver.
How many fish can you have in a tank of a given size? There's no single answer. Think of it as a Rubik's Cube of a space, in which so long as everybody can slide and move and grow in size, and the territorial curmudgeons can continue to chase the kids off the lawn without hurting anybody, you've got a good setup.
