Fish-Only-With-Live-Rock (FOWLR) Aquariums
Drs. Foster & Smith Educational Staff

A fish only with live rock (FOWLR) aquarium is a great way to enjoy some of the most colorful and fascinating marine species. These beautiful but often aggressive fish would create havoc in a confined reef system with invertebrates and live corals, but in a live rock aquarium you can enjoy their unique splendor without worry. Better yet, FOWLR setups are typically less expensive, easier to keep, and less demanding than coral reef aquariums.

Aggressive Beauties
Triggerfish are best known for their striking triangular shape and variety of different colors and patterns. They also swim in an unusual fashion, using their dorsal and anal fins. They earn their name from the first dorsal fin, which has a very strong bone that can be locked into place, helping aid these fish in maintaining a position within rockwork.

Pufferfish have the amazing ability to expand their bodies to over twice the normal size when threatened. They are a slower moving fish with a beak-like mouth and two fused front teeth. Their jaws are extremely strong, which helps them feed on their favorite food, crustaceans. These fish are very personable, and will learn in time to feed directly from their owner's hand.

Because aggressive fish will destroy delicate live corals, we used some beautiful, life-like artificial corals in our aquarium. They will withstand abuse and do not require the effort and care level of their counterparts.

Large Angelfish are very colorful and hardy. They have interesting swimming patterns that can add appeal to your aquarium. Many species of angels will also help control algae as they continually graze upon the rocks.

Tangs, commonly referred to as Surgeonfish or Doctorfish, have small scales and one or more scalpel-like spines on each side of the tail. These spines are used in aggression and for defense. Tangs appreciate hiding places, plenty of room to swim, and a diet of algae and dried seaweed.

Wrasse are best known for their bright colors, elongated body, and pointed snout. Some Wrasse will pick parasites and dead tissue from larger fish, including predators. Most Wrasse bury themselves in the sand at night, and also when threatened.

FOWLR Set-up Tips

  1. Choose the largest aquarium that is appropriate for its intended location; ideally a 6-foot setup or larger is recommended.
  2. FOWLR aquariums require an efficient biological filter due to the size and the quantity of fish. A great choice in filter is a wet/dry, or a sump/refugium.
  3. Along with the filtration, an efficient protein skimmer is needed to help control nutrients within the system. For smaller aquariums, the SeaClone or Prizm skimmers are a great choice. Live Rock
  4. Choose a lighting system that provides between 1 to 2 watts of light per gallon. Keep the lighting on the low side of the recommendation if the room is not air-conditioned.
  5. Every FOWLR aquarium starts with a sand bed. Sand beds add aesthetic appeal, aid in filtration and pH buffering, provide a habitat for burrowing fish, and help seat and stabilize your live rock. Seaflor Special Grade Reef Sand is a good choice when combined with either Arag-Alive or live sand from
  6. The live rock for this type of aquarium needs to be very porous. Fiji, Lalo, and Tonga are all good choices. Live rock will need to cure with the filtration in operation for about 2 to 4 weeks, until the ammonia and nitrite levels are zero, before you can add fish.
  7. Stock your aquarium gradually over a period of a few months, introducing an entire species group at a time, in order from the least to most aggressive species. This will allow your fish to become accustomed to the aquarium and will reduce aggression as other fish are added.

With all of the different species available to the hobbyist today, a FOWLR aquarium can prove to be an exciting aquarium that will bring years of enjoyment.

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