Paragraph:Aquariu.ms highly recommends the usage of AqAdvisor to get the correct stocking levels for your specific setup size, equipment used, and other aspects. Please note that this website does have into effect a conservative view when calculating the stocking levels and water change levels. This tool will also allow you to be able to see if species require different water parameters, or in some cases, they might be each other prey in the wild.
There are three distinct different zones where all inhabitants are classified within as they will most likely tend to be visible in these areas. By stocking your aquarium to have all of these zones filled, you can make an aquarium look completely stocked full of active fish when in reality you are still within or below stocking limits. Plus when you have all three zones covered, you will have the various natural effects and benefits that each species has when coexisting with each other. We will go over some of the most common traits that are found within species of each zone, along with many benefits of having those in the given zone and why they are placed into these zones.
The top zone of the aquarium is normally one that will be the most noticeable when someone looks into your aquarium, and for obvious reasons. Without anything moving in the top section, it might seem like most of your inhabitants are hiding, scared, or it may also appear as if your aquarium is not stocked all the way. Decorations might curb this initial thought if they are placed correctly, it still is the first place that many people's eyes glow towards when they first see an aquarium. To tell if a fish belongs in this zone, we can most easily tell by the shape and direction of their mouth. Commonly we will see that they have a mouth that is on the top of their face and it should be shaped upward towards the surface of the water. This is because these fish will eat directly from the surface in the wild, and need to have these adjustments to catch food or prey sitting on the water's surface. Other less common traits found in top zone fish would be the fact that they stay still in the water towards the surface, and sometimes more obviously will only stay in the top zone when viewed in various aquariums. When fish in this zone are sleeping they will tend to drift around the aquarium, however many that need to breathe oxygen with their labyrinth organ will sink at the bottom of the aquarium and periodically swim to the surface to get the oxygen they require.
The middle zone of the aquarium is one that holds most of the fish species and is one that is most commonly used when stocking an aquarium. Commonly we see that many fish in this zone will have mouths that are directly in the middle of their body which allows them to eat food that is falling or drifting throughout the water column. Many fish species that are within this zone are schooling or shoaling fish that require a moderate population of their species to feel safe, and will mostly roam around the middle of the aquarium playing with other inhabitants. There are very few invertebrates that can be classified within this zone as they tend to always stay towards the bottom zone compared to the majority of the fish species that are classified within this zone. When fish of this zone are sleeping they will tend to stay floating (or hovering) in the same position the whole night although in some cases they will drift with the water current around the tank carelessly.
The bottom zone of the aquarium is normally one that will contain most, if not all, invertebrates and mostly bottom-feeding fish. This zone is mostly forgotten since decorations cover most of the bottom's surface and also that many aquarium owners do not see the direct benefit of having a cleaning crew for your aquarium. Commonly we see that many fish in this zone will have a mouth that is on the bottom of their body and the fish may have color that looks like camouflage to hide it from other inhabitants. For invertebrates most commonly they will be classified into this zone as without any decoration or walls they would only have this zone since many cannot swim, and if they can swim it is only for a short period. Most of the inhabitants of this zone will feed off of the excess food that is placed into the aquarium during feeding time(s), any algae that may be on the walls of the aquarium or decorations, and some if not all will feed off of any dead inhabit that is resting on the bottom.