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.
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
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 type||Recommended number of saltwater fish in a 100 gallon fish tank||Ok to mix species?|
|Anthias||1-5, 1 male, rest female||Yes, with some minor aggression|
|Blenny||2||Yes, (eg. lawnmower + fang)|
|Cardinalfish||1-9 if you want a shoal||Yes|
|Chromis||1-9 if you want a shoal||Yes|
|Dwarf Angelfish||1 typically, 2 if paired||No|
|Fairy Basslet||1 gamma or 1 blackcap or 3-5 chalk bass||No|
|Pseudochromis||1 typically, 2 if paired||No|
|Reef safe wrasses||1-5 flasher wrasses or a mix of fairy wrasses||Yes, if fairy wrasses|
|Tangs||1 typically||Only advanced, intro same time|
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.)
Other important information
Here are a few other quick tips and tricks to consider when stocking a 100-gallon fish tank.
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:
|Manufacturer||Model||Tank Dimensions (inches)||Tank + Stand (inches)||Tank volume||Total system volume|
|Innovative Marine||INT 100||47.3 x 23.6 x 19.7||47.3 x 23.6 x 55.51||100 gal||100 gal|
|Innovative Marine||INT 100 Peninsula||47.2 x 30 x 16.1||47.2 x 30 x 51.5||100 gal||100 gal|
|Innovative Marine||INT 112 Lagoon||35.4 x 35.4 x 19.7||35.4 x 35.4 x 55.51||112 gal||112 gal|
|Waterbox||Reef 100.3||35.4 x 23.6 x 21.7||35.4 x 23.6 x 57||71.7 gal||100.3 gal|
|Waterbox||Reef 130.4||47.2 x 23.6 x 21.7||47.2 x 23.6 x 57||96.3 gal||130.3 gal|
|Waterbox||Marine X110.4||47.2 x 19.7 x 21.7||47.2 x 19.7 x 57.1||79.6 gal||110.4 gal|
|Waterbox||INFINIA 125.3||40.9 x 23.6 x 22.6||40.9 x 23.6 x 60.6||85.9 gal||125.3 gal|
|Waterbox||INFINIA 165.4||48.8 x 25.3 x 23.6||48.8 x 25.3 x 61.6||114.5 gal||114.5 gal|
|Red Sea||Max S 400||41 x 27.5 x 25||41 x 27.5 x 61||97 gal||110 gal|
|Red Sea||Reefer 425 G2||47 x 23.6 x 22||47 x 23.6 x 56||91 gal||125 gal|
|Red Sea||Reefer XL 425||46 x 22.6 x 22||47 x 22.6 x 56||88 gal||112 gal|
|Red Sea||Peninsula 500||49.2 x 23.6 x 23.6||49.2 x 23.6 x 63||105 gal||132 gal|
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.
|Manufacturer||Model||Tank weight empty (pounds)||Tank weight filled w/ saltwater (pounds)||Tank + cabinet + saltwater weight (pounds)|
|Innovative Marine||INT 100||265||1120.6||1212.6|
Equipment needed to run a 100-gallon fish tank
- MP-40 or Gyre pump
- Protein skimmer
- Test kits
- Lid or mesh netting
- Quarantine tank