Best saltwater fish for a 100-gallon tank

75 Best saltwater fish for a 100-gallon fish tank

How to determine the best fish for a 100-gallon tank

A 100-gallon fish tank is a great size that will allow you to keep a variety of very cool and colorful saltwater fish. The selection of fish is going to be similar to the 90-gallon tank recommendations, because the next big breakthrough in livestock happens at the 125-gallon mark.

With this volume, you will be able to have a combination of open-water swimmers like tangs, dwarf angelfish, and reef-safe wrasses, substrate dwellers like the Diamond goby and site attached/perching fish, like Clownfish, cleaner gobies, and Hawkfish, to highlight a few options.

Flasher wrasse

The 75 best saltwater fish for a 100-gallon fish tank

There are a lot of amazing, colorful reef fish, but not all are a great fit for every tank. Here is a list of the 75 best saltwater fish for a 100-gallon fish tank:

  • Antias: Lyretail, Dispar
  • Blenny: Tailspot, Two-spot, Canary, Midas, Striped, Harptail, or Smith’s
  • Cardinalfish: Banggai, Yellow, Pajama, or Longfin
  • Chromis: Blue-green or Blue Reef
  • Cleaner goby: Neon, Yellow line, Shark nose, or Hybrid
  • Clownfish: Tomato, Cinnamon, Maroon, Clarkii, Spotcinctus, Ocellaris, Percula, Orange skunk or Pink skunk
  • Dartfish: Firefish, Purple firefish, Zebra, Scissortail or Helfrichi
  • Dwarf Angelfish: Flame angel, Coral Beauty, Bi-color, Pygmy/Cherub, Flameback, Lemonpeel, Rusty, Red Stripe,
  • Fairy Basslet: Blackcap, Chalk basslet or Royal Gramma
  • Fancy goby: Clown, Court jester, Diamond, Two-spot, or Yasha
  • Filefish: Aiptasia-eating
  • Hawkfish: Falco, Flame, or Longnose
  • Marine betta
  • Pseudochrois: Neon or Orchid
  • Reef Safe Wrasses: Mystery, Exquisite, Bluehead, Scotts, Katherine’s, Carpenter’s, Fairy, McCosker’s, Melanurus, Yellow Coris, Sixline
  • Tangs: Yellow, Convict, Mimic, Kole, Tomini, Two-spot Bristletooth, Squaretail Bristletooth,

dwarf lionfish: Fuzzy dwarf, Dwarf Zebra, Fu Manchu, or Mombasa

Firefish in a saltwater tank

How many fish can be kept together in a 100-gallon tank?

A 100-gallon tank could safely house approximately 18-25 compatible, appropriately sized community saltwater fish. Exactly how many fish will depend on the relative size of chosen fish as well as the desired maintenance difficulty level, which increases with the number of fish in the tank.

Fish typeRecommended number of saltwater fish in a 100 gallon fish tankOk to mix species?
Anthias1-5, 1 male, rest femaleYes, with some minor aggression
Blenny2Yes, (eg. lawnmower + fang)
Cardinalfish1-9 if you want a shoalYes
Chromis1-9 if you want a shoalYes
Cleaner goby1No
Dwarf Angelfish1 typically, 2 if pairedNo
Fairy Basslet1 gamma or 1 blackcap or 3-5 chalk bassNo
Fancy goby1No
Marine betta1N/A
Pseudochromis1 typically, 2 if pairedNo
Reef safe wrasses1-5 flasher wrasses or a mix of fairy wrassesYes, if fairy wrasses
Tangs1 typicallyOnly advanced, intro same time
best saltwater fish for a 100-gallon fish tank


A few brief, but important notes about compatibility:

  • Personal experience and shared experiences of others suggests it is challenging to keep shoals of fish alive in a saltwater tank. There is often aggression between fish of the same species that leads to dwindling of the shoal until a single fish or bonded pair remain. But a 100-gallon fish tank may be the size needed to succedd.
  • Even though the list above says you can have 1 Fairy Basslet and 1 Pseudochromis dottyback, that is an either/or decision. They won’t get along together.
  • Dartfish are great saltwter fish. They will do well in a tank this size, as long as the other inhabitants are are also peaceful. They may be bullied by more aggressive fish.
  • Hawkfish are not compatible with mobile invertebrates (crabs, shrimp, snails, etc.)

Learn more about saltwater fish compatibility here.

Other important information

Here are a few other quick tips and tricks to consider when stocking a 100-gallon fish tank.

Marine betta saltwater fish

Importance of quarantine

Quarantine is a critically important process when you have a fish tank that is as large as a 100-gallon tank. You will be adding a lot of fish, at different times and from various sources. Each new addition to the tank is a potential source of parasites that can crash your tank.

If you do introduce parasites to your tank, it can be extremely difficult to deal with, due to the size of the tank and the challenges with removing the fish for treatment.

Dealing with aggression

Aggression is another important consideration when building the perfect 100-gallon saltwater fish tank. When stocking the aquarium, start with the most timid fish first, and then work you way through your ideal list progressing towards the more aggressive fish. Adding the more aggressive fish last will help improve the compatibility overall.

100-gallon fish tank dimensions

The dimensions of a 100-gallon fish tank will vary significantly, based on the manufacturer, model, overall shape, and whether the volume calculated is the desired display tank volume or system total volume.

Here is a table with dimensions listed for some of the most popular models in the 100-gallon range:

ManufacturerModelTank Dimensions (inches)Tank + Stand (inches)Tank volumeTotal system volume
Innovative MarineINT 10047.3 x 23.6 x 19.747.3 x 23.6 x 55.51100 gal100 gal
Innovative MarineINT 100 Peninsula47.2 x 30 x 16.147.2 x 30 x 51.5100 gal100 gal
Innovative MarineINT 112 Lagoon35.4 x 35.4 x 19.735.4 x 35.4 x 55.51112 gal112 gal
WaterboxReef 100.335.4 x 23.6 x 21.735.4 x 23.6 x 5771.7 gal100.3 gal
WaterboxReef 130.447.2 x 23.6 x 21.747.2 x 23.6 x 5796.3 gal130.3 gal
WaterboxMarine X110.447.2 x 19.7 x 21.747.2 x 19.7 x 57.179.6 gal110.4 gal
WaterboxINFINIA 125.3 40.9 x 23.6 x 22.640.9 x 23.6 x 60.685.9 gal125.3 gal
WaterboxINFINIA 165.448.8 x 25.3 x 23.648.8 x 25.3 x 61.6114.5 gal114.5 gal
Red SeaMax S 40041 x 27.5 x 2541 x 27.5 x 6197 gal110 gal
Red SeaReefer 425 G247 x 23.6 x 2247 x 23.6 x 5691 gal125 gal
Red SeaReefer XL 42546 x 22.6 x 2247 x 22.6 x 5688 gal112 gal
Red SeaPeninsula 50049.2 x 23.6 x 23.649.2 x 23.6 x 63105 gal132 gal
100-gallon tank dimensions will vary by manufacturer and model

How heavy is a 100-gallon tank?

A 100-gallon fish tank can way 1,200 pounds or more, when you include the tank, cabinet and weight of the saltwater. Even more when you add rock and a sump. Below is a table to illustrate the total weight based on manufacturer provided weight data and an estimate of 8.556 lbs per gallon of saltwater.

ManufacturerModelTank weight empty (pounds)Tank weight filled w/ saltwater (pounds)Tank + cabinet + saltwater weight (pounds)
Innovative MarineINT 1002651120.61212.6
Purple tang fish

Equipment needed to run a 100-gallon fish tank

  • Lights
  • Heater
  • Chiller
  • MP-40 or Gyre pump
  • Sump
  • Protein skimmer
  • Test kits
  • Lid or mesh netting
  • Quarantine tank

Stocking options other than fish

Not sure if 100-G is the right size? Check out these other stocking guides





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