What is a Reef Tank?

Aquarium reef tank
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Simply put, a "reef tank" is the closest thing to the reefs in the ocean that you can put in a glass box. Due to the size difference, the things you put in your reef tank have to be able to get along with each other. In the ocean, a species that is being predated by something can move or migrate to a safer area. In a closed system like your 55g tank, the opportunity to flee is greatly limited. For this reason, the critters that you put in your reef tank have to be able to get along with each other.

With a little research, you can build a piece of the reef with critters that not only can get along together but in many cases form a symbiotic relationship with each critter, helping another to thrive. The relationship of a Clownfish and its host anemone is a perfect example of this. The Clownfish is protected by the stinging tentacles of the anemone while the Clownfish brings the anemone food in the form of small fish that it captures as well as the detritus that it deposits in the anemone.

A Reef Tank System is a Fish Only With Live Rock system with corals which requires a higher quality lighting system as well as a higher water quality and movement. A sustainable healthy reef tank also requires occupants which do not adversely affect corals:

  • Reef Safe Fish are those that do not pick at corals or eat invertebrates. They also are not aggressive towards other fish.
  • Reef Safe Invertebrates are those which do not consume corals, which are an integral part of a true reef tank, setting it apart from a Fish Only With Live Rock tank.
  • Reef Safe Tank Janitors, when properly selected, are amazing. They can cut your tank maintenance chores down to near zero. There are critters that will keep your aquarium glass clean, other that will keep your substrate free of uneaten food and detritus and get fat in the process. 


Since corals are included in a reef tank system, sufficient lighting for the corals must be provided. The generally accepted "rule of thumb" for reef tank lighting is 3.5 watts per gallon of tank water for most soft corals and 4.5 watts (of fluorescent light) per gallon of tank water for hard (SPS & LPS) corals.


Since most corals do not tolerate the levels of nitrates, phosphates and other toxins that most fish and invertebrates will withstand, water quality in a reef tank is of utmost importance. While most of the expensive "state of the art" filtration systems work well at removing toxins, they are not, by any means, required.

With the advances in science and innovation, Mini Reef Tanks are becoming more and more popular. Many reef tank aquarists design their own reef tank filtration systems using one or a combination of a number of different filters to attain the desired results.

Reef Ready Aquariums

"Reef Ready" Aquarium systems, which have the appropriate lighting and filtration already in place are available on the market today. These systems simplify the process of assembling a reef tank system. If you want to simplify the process of designing and assembling a reef tank, these top gallon aquariums are some of the aquarium packages which work well for reef systems.


While most corals require a high level of water quality and lighting, there are those easy corals that are less demanding, requiring a lower light level and/or a lower water quality level, allowing novice reef tank keepers to attain success. The downside to the smaller tanks is that, when something goes wrong in the tank, it happens pretty fast, leaving little time to correct the problem before it turns into a disaster. With the advances in the science of keeping corals and reef tank system designs, creating and maintaining a healthy reef tank is within almost anyone's reach.