Sometimes it’s just easier to look at a chart and move on.  For more detail about a compatibility component visit the compatibility discussions.  These charts are for freshwater and saltwater fish providing a summary of the compatibility information and more.

Each chart can be enlarged and zoomed into to see a specific fish or compatibility value.

The compatibility chart identifies compatibility in two ways.  The first is that of similarity.  If the fish have similar traits then it is assumed they would be compatible.  The other is when combining different types of fish and different traits.  Two fish can be termed compatible if they have dissimilar traits and will not compete for resources in the aquarium.

The scoring method below will help to understand the chart.

The four compatibility traits are: Aggressive, Calm, Social/Schooling, Reclusive/Hiding.  They are more fully understood as:

• Aggressive: May not get along well with other aggressive or reclusive fish.
• Calm: Generally gets along with all types of fish.
• Social/Schooling: Prefers to be with other social/schooling fish, but can get along with calm and reclusive fish.
• Reclusive/Hiding: Prefers to be alone or with other reclusive/hiding fish, may not get along with aggressive fish.

The scoring method looks at these traits and uses the following values in scoring a trait:

• 3: Highly Compatible
• 2: Compatible
• 1: Slightly Compatible
• 0: Not Compatible

Using the traits and scoring method, the following matrix show them in use.

The Diet compatibility chart identifies compatibility in two ways.  The first is that of similarity.  If the fish have similar diets then it is assumed they would be compatible.  The other is when combining different types of fish and different diets.  Two fish can be termed compatible if they have dissimilar diets and will not compete for resources in the aquarium.

The scoring method below will help to understand the chart.

The four diet types are: Flakes, Invertebrates, Plant matter & Algae, and Biofilm Protozoa and Insect larvae.  Since many fish are omnivores it is difficult to relegate them too a single type of food.  Rather, the fish are assigned a numerical score that represents a preference for a type of food, and the preference is used to determine compatibility.

The three compatibility/preference scores are:

• 3: Dark Blue, Highly Compatible
• 2: Medium Blue, Compatible
• 1: Light Blue, Slightly Compatible

Note: when two different diets are present in the same aquarium, the aquarium needs to be of sufficient size to accommodate two different fish with two different diet requirements.

The Environmental Compatibility chart looks at the physical environments of Cave Dwelling and Open Water fish.  Compatibility is identified in two ways.  The first is that of similarity.  If the fish have similar environmental preferences then it is assumed they would be compatible.  The other is when combining different types of fish and different environment preferences.  Two fish can be termed compatible if they have dissimilar preferences and will not compete for physical space resources in the aquarium.

The scoring method below will help to understand the chart.

The two environment preference types are: Cave Dweller and Open Water.  Most fish have a definite preference that is intertwined with their genetics and overall behavioral characteristics.  Fish are adept at moving and hiding from predators in their preferred environment.

The two preferences represented in the chart are:

Cave Dweller: Fish that prefer hiding spots and shaded areas, often staying close to rocks, caves, or plants.

Open Water: Fish that prefer swimming freely in open spaces.

The chart is generated using numerical values representing compatibility, they are:

• 3: Highly Compatible (Both fish prefer the same environment) RED
• 2: Compatible (One fish prefers open water while the other is indifferent) MEDIUM RED
• 1: Slightly Compatible (One fish prefers caves while the other prefers open water) LIGHT RED
• 0: Not Compatible (Not applicable in this case as we have only two environmental characteristics)

The compatibility matrix represented in the chart looks at each species and identifies their preference.  The chart then presents this preference in relation to other fish species that have also been scored.  The chart follows the matrix example below.

Note: when two different preferences are present in the same aquarium, the aquarium needs to be of sufficient size and sufficient architecture to accommodate different fish with  different environment requirements.

The Illumination Compatibility chart looks at the number of hours of illumination that fish prefer or do best under.  Generally the number of illumination hours will vary between 8 hours and 16 hours of daylight in a natural setting.  This roughly corresponds to hours of daylight at the equator and spreading outward either north or south of the equator where aquarium fish are found.

A fish that is determined to be compatible is one that shares the same preference for hours of illumination.  Fish can be termed incompatible if they have dissimilar preferences for illumination of  the aquarium.

The chart was created using the two extremes of 8 and 16 hours of illumination.  The illumination preference for each fish was established and then compared with other fish.  The compatibility score is as follows:

• 3: Highly Compatible (Both fish have the same illumination preference) DARK BLUE
• 1: Slightly Compatible (Fish have different illumination preferences) LIGHT BLUE

The compatibility matrix represented in the chart looks at each species and identifies their illumination preference.  The chart then presents this preference in relation to other fish species that have also been scored.  The chart follows the matrix example below.

Note: There can be a considerable difference between species’ preference for illumination.  THe chart represents a mid aquarium illumination measurement.  Species that prefer cave dwelling will have a different illumination tolerance, but generally they will still have an illumination preference of between 8 and 16 hours albeit at a reduced lumen level.

The pH Compatibility chart examines the water pH that fish prefer or do best under.  Generally the pH variance between fish species is very small, but becomes significant in the overall health of the fish and the presentation of their natural behaviors in breeding and socializing.  The pH range for fish generally falls between 5 and 9, about two points from neutral 7 pH.

Compatibility is represented as those fish that prefer the same pH level, or deviate not more than .5 points.  Incompatibility is represented by those fish that have a preference that separates them by a full point.  This chart is not intended to present the actual pH preference value  for each fish.

The compatibility score is as follows:

• 3: Highly Compatible (Both fish have the same pH preference) DARK PURPLE
• 2. Compatible (Both fish are within .5 pH of one another) PURPLE
• 1: Slightly Compatible (Both Fish have different pH preference) WHITE

Note: pH is one of the more important water chemistry values to be aware of.  The sensitivity of fish species to pH levels is significant.  Although a fish can survive in an aquarium with changing pH levels, they can do so for only a short time.  A fish’s health will rapidly deteriorate when in aquarium water that is not optimized for their preferred pH level.

The Swimming Realm Compatibility chart examines the location within the aquarium (realm) within which a fish likes to swim or inhabit. Many fish have specific depths from the water surface in which they forage for food, protect themselves from predators, and reproduce.  The Swimming Realm Chart compares one species against another to establish compatibility compatibility.

Compatibility is determined by fish preferring the same swimming realm.

To make the comparison between species each fish is examined to establish the their depth preference.

1. Upper Tank Near Surface: Fish that prefer to swim near the surface of the water.
2. Mid Tank: Fish that prefer to swim in the middle of the tank.
3. Lower Tank Bottom: Fish that prefer to stay near the bottom of the tank.

A compatibility score is then assigned that represents the species interaction with other species in their swimming realm.

• 3: Highly Compatible (Both fish prefer the same swimming realm) AMBER
• 1: Slightly Compatible (Fish prefer different swimming realms) LIGHT AMBER

Note: Swimming Realm Compatibility  is a way of making better use of the aquarium vertical space.  If all the fish were bottom swimmers the aquarium would be out of balance from a population point of view.  Using the Swimming Realm Compatibility chart gives the aquarist a means of increasing the population of the aquarium without increasing competition among species.

The compatibility matrix is represented below.

The Vegetation Preference Compatibility chart examines the type of vegetation and fish species behavior with the vegetation.  Many fish have specific biological requirements that relate to a type of vegetation.  The vegetation examined in this chart is either dense or sparse in its tank presence.  Depending on the size of the vegetation present, a top swimmer can become a mid tank swimmer.  So, there can be some behavioral changes presented depending on vegetation.

Compatibility is determined by the density of vegetation and the fish’s propensity to make use of the foliage.  A sparsely populated tank with vegetation provides for longer views and gives strong swimmers a long path to swim through.  Whereas, a dense vegetation tank provides for better protection from predators and many locations for egg-laying.

Compatibility is determined by fish preferring the same amount of foliage.

To make the comparison between species each fish is examined to establish the their vegetation preference.

1. Dense Vegetation: Fish that prefer living in environments with a lot of plants and foliage.
2. Sparse Vegetation: Fish that prefer living in environments with few or no plants.

A compatibility score is then assigned that represents the species interaction with the vegetation.

• 3: Highly Compatible (Both fish prefer the same vegetation condition) DARK BROWN
• 1: Slightly Compatible (One fish prefers dense vegetation while the other prefers sparse vegetation) LIGHT BROWN

Note: This chart is applicable to those species that interact with vegetation.  Not all fish are interested in vegetation.  Some cave-dwellers do not make use of vegetation at all.  Consider the vegetation chart one that is somewhat specialized to certain species.

The compatibility matrix is represented below.

The Water Flow Compatibility chart examines the type of water flow fish prefer.  Many fish have specific biological requirements that require a water flow in their natural habitat.  Some, on the other hand, are better suited to stagnant pools with little to no water flow.  Often water flow preference is related to spawning and food types.

Compatibility is determined by similar types of water flow.  Fish species that prefer turbulent water may not exhibit natural behaviors if placed in a stagnant water environment.

There are two main conditions that are represented in this chart:

1. High Turbulence Water: Fish that prefer living in environments with strong water currents.
2. Stagnant Water: Fish that prefer living in calm or still water environments.

A compatibility score is then assigned that represents the species preference for water flow.

• 3: Highly Compatible (Both fish prefer the same water flow condition)DARK GREY
• 2: Compatible (One fish prefers high turbulence water while the other is indifferent)GREY
• 1: Slightly Compatible (One fish prefers high turbulence water while the other prefers stagnant water)LIGHT GREY

Note: There are many factors that play into water flow.  The age of fish, the species, predators, the list goes on.  This chart is representative of aquarium fish with moderate turbulent water.  The amount of turbulence considered to be high turbulence is that which can be generated through the use of power-head equipment.  If greater turbulence is needed there are other types of external pumps and water take-up devices that can be used. 

Generally speaking, most aquarium fish enjoy water flow of some kind. 

The compatibility matrix is represented below.

The Water Hardness Compatibility chart examines the water hardness fish prefer.  Many fish have specific biological requirements for higher calcium and magnesium levels in their natural habitat.  Some, on the other hand, are better suited to lower concentrations.  The amounts of these chemicals in the water can influence breeding and reproduction.

Compatibility is determined by similar types of water hardness represented using dGH as the measurement scale.

To create this chart the dGH preference was established for each species of fish.

Then a compatibility score was assigned that represents the species preference for dGH.

• Dark Green: Highly Compatible (Score: 3)
• Medium Green: Compatible (Score: 2)
• Light Green: Slightly Compatible (Score: 1)

Note: While there is a significant range of dGH that a fish can exist within, There is a preference level that should be observed.  This chart shows the preference between fish species and does not show the value of dGH that each fish preferred.

The Water Temperature Compatibility chart examines the water temperature fish prefer.  Many fish have specific biological requirements for ranges of temperature in their natural habitat.  The temperature of water can influence general health, breeding, and activity.  So, it is important to keep temperatures of the aquarium constant with only slight variances.

Compatibility is determined by similar water temperatures and represented using the Celsius scale.

To create this chart the dGH preference was established for each species of fish.

Then a compatibility score was assigned values indicated below.

• Dark Amber: Highly Compatible (Score: 3)
• Medium Amber: Compatible (Score: 2)
• Light Amber: Slightly Compatible (Score: 1)

Note: There will always be some variation in water temperature in an aquarium.  The variation usually will not exceed a full degree.