The X inches of fish per gallon rule is pretty rampent and, in my opinion, is a bad way to determine the size and type of fish for your tank. Most people suggest anywhere from one inch of fish a gallon to one inch for every ten gallons. This thread is to suggest how to properly select fish for your aquarium. It goes over types of fish, curbing aggression and stocking limits for tanks.
TYPES OF FISH:
This section is for selecting types of fish and how large they can be relative to the tank size. This also covers common fish found within these categories.
ACTIVE SWIMMERS:
This type of fish is the most outgoing of all the fish. They move constantly and generaly spend most of their time out in the open. These fish make up the centerpeices to our tanks and on tanks less than 100 gallons, with some exceptions, I would suggest keeping only one species per tank. These fish tend to be larger and can be too active for smaller tanks and most should be kept in a tank of 40 gallons or larger depending on the species. Common fish in this categorie are:
Angelfish, Large and Dwarf
Anthias
Butterflyfish
Chromis
Large Damsels
Filefish
Rabbitfish
Groupers
Hogfish
Tangs
Large Wrasses
Large Puffers
To select fish from this category take the smallest side on your tank and divide by 4, this value is the largest fish in this category you should keep in your tank. So, for example, the shortest side on a common 55 gallon tank in 12 inches, so the largest active swimmer should be no larger than three inches. That being said a 40 gallon breeder has a shortest side of 18 inches, so the largest fish in a tank of that size should be no longer than 4.5 inches.
SEMI-ACTIVE SWIMMERS:
This type of fish are generaly less active and spend most of their time bolting from hole to hole. Some of these fish are schooling and more of this type of fish can be kept in a smaller tank. These fish make up the flowing activity in our tanks and in smaller tanks can be the centerpeice. These fish should generaly be kept in tanks larger than 30 gallons or larger depending on the species. Common fish in this categorie are:
Basslets/Grammas
Boxfish
Cardinalfish
Smaller Chromis
Clownfish*
Smaller Damsels
Dartfish
Dottybacks
Smaller Puffers
Smaller Wrasses
To select fish from this category, take the smallest side of the tank and divide by 3. So in a 55 gallon the largest active swimmer should be no larger than 4 inches, and on a 40 gallon breeder no larger than 6 inches.
*Clownfish can also be a surface dweller, which you will read about next.
SURFACE DWELLERS:
These fish tend to live on the bottom of your tank and on the rockwork. Many of these fish lack a swimbladder, making it hard for them to stay aloft in the water column. These fish are the little hidden gems away from our bigger, flashy fish. They can also provide helpful services to our tanks, like the algae blenny or neon goby. These fish can be kept in tanks as small as 10 gallons but some require live food and need a larger tank. Common fish in this category are:
Anglers
Blennys
Clownfish*
Dragonets
Eels
Gobies**
Hawkfish
Lionfish
To select fish from this category, take the shortest side of your tank and divide by 2, so in a 55 gallon the largest Surface Dweller should be no larger than 6 inches, and in a 40 gallon breeder no larger than 9 inches.
*Clownfish, when associated with an anemone, will rarly leave it, ususaly only to feed, and larger clowns can be kept in smaller tanks
**Shrimp Gobies are not Surface Dwellers
SUBTERRANEAN RESIDENTS:
This small list of fish generaly live burrowed. Fish in this category can burrow under rocks, causing them to collapse, and all rockwork should be applied directly to the bottom. Territorial issues can be a problem if different species are housed in smaller tanks. They also work well in nano and pico reef tanks. It is also important to have fine sand at least 4 inches deep for some species. Common fish in this category are:
Shrimp Gobies
Engineer Goby
Jawfish
To select fish from this category take the smallest side of your tank and divide by 2, so in a 55 gallon the largest Surface Dweller should be no larger than 6 inches, and in a 40 gallon breeder no larger than 9 inches.
CARRYING CAPACITY:
To find the most fish you can keep in your tank is somewhat tricky. Active Swimers are going to need more room than a Semi-Active swimmer, and thus take up more of your carrying capacity. The best thing I have found is that you have whatch the fish. Observe what holes they like and what their territories are. If you think all the territory in the tank is taken, don't add anymore fish. You will generaly run out of territory before you fill your carrying capacity
CURBING AGGRESSION:
Fish in different categories will take different territories and larger, more agressive fish will bully smaller fish trying to occupy the same space. Fish should be added in the order of least agressive to most agressive. Semi-active fish should be added first, followed by surface dwellers, then the subterranian residents and lastly by the active swimmers.
As always research everything you intend to keep, form a plan and stick to it. Most often problems arise from impulse buys. ReefCentral members are always here 24/7 to help if you have questions....Happy fishkeeping!!!
TYPES OF FISH:
This section is for selecting types of fish and how large they can be relative to the tank size. This also covers common fish found within these categories.
ACTIVE SWIMMERS:
This type of fish is the most outgoing of all the fish. They move constantly and generaly spend most of their time out in the open. These fish make up the centerpeices to our tanks and on tanks less than 100 gallons, with some exceptions, I would suggest keeping only one species per tank. These fish tend to be larger and can be too active for smaller tanks and most should be kept in a tank of 40 gallons or larger depending on the species. Common fish in this categorie are:
Angelfish, Large and Dwarf
Anthias
Butterflyfish
Chromis
Large Damsels
Filefish
Rabbitfish
Groupers
Hogfish
Tangs
Large Wrasses
Large Puffers
To select fish from this category take the smallest side on your tank and divide by 4, this value is the largest fish in this category you should keep in your tank. So, for example, the shortest side on a common 55 gallon tank in 12 inches, so the largest active swimmer should be no larger than three inches. That being said a 40 gallon breeder has a shortest side of 18 inches, so the largest fish in a tank of that size should be no longer than 4.5 inches.
SEMI-ACTIVE SWIMMERS:
This type of fish are generaly less active and spend most of their time bolting from hole to hole. Some of these fish are schooling and more of this type of fish can be kept in a smaller tank. These fish make up the flowing activity in our tanks and in smaller tanks can be the centerpeice. These fish should generaly be kept in tanks larger than 30 gallons or larger depending on the species. Common fish in this categorie are:
Basslets/Grammas
Boxfish
Cardinalfish
Smaller Chromis
Clownfish*
Smaller Damsels
Dartfish
Dottybacks
Smaller Puffers
Smaller Wrasses
To select fish from this category, take the smallest side of the tank and divide by 3. So in a 55 gallon the largest active swimmer should be no larger than 4 inches, and on a 40 gallon breeder no larger than 6 inches.
*Clownfish can also be a surface dweller, which you will read about next.
SURFACE DWELLERS:
These fish tend to live on the bottom of your tank and on the rockwork. Many of these fish lack a swimbladder, making it hard for them to stay aloft in the water column. These fish are the little hidden gems away from our bigger, flashy fish. They can also provide helpful services to our tanks, like the algae blenny or neon goby. These fish can be kept in tanks as small as 10 gallons but some require live food and need a larger tank. Common fish in this category are:
Anglers
Blennys
Clownfish*
Dragonets
Eels
Gobies**
Hawkfish
Lionfish
To select fish from this category, take the shortest side of your tank and divide by 2, so in a 55 gallon the largest Surface Dweller should be no larger than 6 inches, and in a 40 gallon breeder no larger than 9 inches.
*Clownfish, when associated with an anemone, will rarly leave it, ususaly only to feed, and larger clowns can be kept in smaller tanks
**Shrimp Gobies are not Surface Dwellers
SUBTERRANEAN RESIDENTS:
This small list of fish generaly live burrowed. Fish in this category can burrow under rocks, causing them to collapse, and all rockwork should be applied directly to the bottom. Territorial issues can be a problem if different species are housed in smaller tanks. They also work well in nano and pico reef tanks. It is also important to have fine sand at least 4 inches deep for some species. Common fish in this category are:
Shrimp Gobies
Engineer Goby
Jawfish
To select fish from this category take the smallest side of your tank and divide by 2, so in a 55 gallon the largest Surface Dweller should be no larger than 6 inches, and in a 40 gallon breeder no larger than 9 inches.
CARRYING CAPACITY:
To find the most fish you can keep in your tank is somewhat tricky. Active Swimers are going to need more room than a Semi-Active swimmer, and thus take up more of your carrying capacity. The best thing I have found is that you have whatch the fish. Observe what holes they like and what their territories are. If you think all the territory in the tank is taken, don't add anymore fish. You will generaly run out of territory before you fill your carrying capacity
CURBING AGGRESSION:
Fish in different categories will take different territories and larger, more agressive fish will bully smaller fish trying to occupy the same space. Fish should be added in the order of least agressive to most agressive. Semi-active fish should be added first, followed by surface dwellers, then the subterranian residents and lastly by the active swimmers.
As always research everything you intend to keep, form a plan and stick to it. Most often problems arise from impulse buys. ReefCentral members are always here 24/7 to help if you have questions....Happy fishkeeping!!!
