Types of Reef Tanks

If you recognized the picture link that brought you here as a freshwater tank and not a reef tank – you passed your first pop quiz.  Actually it is a paludarium tank, but we’ll save that bit of trivia for the final exam.

I like to think of reef tanks as falling into 3 basic types.

  • Low demand systems
  • Moderate demand systems
  • High demand systems.

The demand level relates to the water quality and lighting demands of the specimens that you want to keep; the demands placed on the aquarist to maintain the system chemistry; as well as the demands put on the aquarists pocketbook.

When setting up your first tank, it is helpful to know what your end goal is since some of the equipment required for the various setups is different. For instance, if you buy a lighting system for a low demand tank and then decide you want to change to a high demand tank, you will probably need to upgrade your lighting and that can be expensive. Everyone goes through this to some extent, but the more that you can avoid it, the more money you will save yourself in the long-run.

Cost may help you decide on which type of tank to setup.  Low demand lagoon or soft coral tanks can be significantly less expensive to setup and maintain than high demand SPS and clam tanks.   The size of the tank will also have a direct impact on the setup and operating costs.  Nice reef tanks are never cheap to setup and you should be prepared for this. Failure in this hobby is often a result of trying to go too cheap.   If the budget is really tight, then that usually means limiting the inhabitants you attempt to keep in your tank to ensure that you are able to provide a suitable environment.

Fair warning though, if you are successful in the hobby, it is addictive.  If starting out with a small tank, many and perhaps most people end up upgrading their system at least once.  It’s surprising how quickly a 30 gallon tank can run out of room.

A lot of dollars are also wasted in this hobby in other ways, such as buying specimens that have no chance of survival in your tank, purchasing an ineffectual protein skimmer which quickly has to be replaced, buying a lighting system only to have to upgrade it as your interest change, or buying the next great snake oil on the market for $20 a bottle.  This is a hobby that rewards you for doing your homework before spending your hard-earned money.

There are several different basic types of reef tanks that can be setup. These differences are based primarily around the types of reef critters you want to maintain, how much time you are willing to spend on the hobby and to some extent the money you are willing or able to spend on the hobby.

Low Light tank

Sometimes created accidentally by aquarist moving from freshwater to saltwater who assume that the small fluorescent light and hand-on-back filter that worked in fresh water would also work in a reef tank.

  • Primary inhabitants are low light requiring corals which may or may not be photosynthetic. Typical inhabitants may include mushroom coral, polyps, sun coral, non-photosynthetic gorgonians, sponges, mobile invertebrates and of course fish.
  • Macro algae may or may not grow depending on light intensity.
  • Water flow is low to moderate.
  • Lighting usually consists of NO fluorescent bulbs or similar inexpensive lighting
  • Tank size can be small to large, but usually small
  • Cost is generally low, mainly due to the fact that lighting consists of relatively inexpensive lighting and the livestock for these tanks ‘can’ be on the less expensive side.

This is a low demand system in that it places a low demand on water chemistry, budget and time. Many hobbyists create this type of tank accidentally when they start in the hobby because they do not fully understand the lighting demands of many of the critters that live on the reef. Significant restrictions need to be placed on the corals that are introduced into this tank to ensure that they can survive on the available light.

Inclusion of some types of non-photosynthetic corals other filter feeding invertebrates can increase the demand level since they may require frequent and specialized feeding.  This heavy feeding then puts more demand on the water filtration or water changes to keep organics in the water under control.

Lagoon / Estuary tankEstuary tank

Intentionally simulates the protected lagoon or estuary environment which is a more nutrient rich environment with modest water movement.  These protected areas serve as nurseries for many juvenile fish and are frequented by many of the slower moving fish such as seahorses.

  • Primary inhabitants soft coral and perhaps large stony polyp (LPS) corals.  This type of tank is popular for housing seahorses and pipefish who naturally live in this type of environment.
  • Macroalgae is usually a component of this system.
  • Water flow is low to simulate lagoon type conditions.
  • Lighting of moderate intensity is generally used such as high powered fluorescent, small metal halide or LED.
  • Tank size is flexible and a small tank works well for this ecosystem especially if difficult to feed specimens are kept such as seahorses.
  • Cost is potentially low as expensive equipment such as a skimmer or calcium reactor are not required and lighting can be fairly modest.

This is also  a ‘Low Demand’ system

Soft and LPS Reef Tank

Soft Coral and Large Polyp Stony (LPS) Coral tank

  • Primary inhabitants are soft corals and LPS with enough lighting to support any photosynthetic soft corals or LPS corals that are desired to be kept.Moderate light clams may also be included, as well as mobile invertebrates and fish.
  • Macro algae is usually excluded as it may become a nuisance, but some people like the look it adds to the tank.
  • Water flow is moderate to simulate a reef slope condition. A wave maker of some type may be used to give somewhat turbulent water flow.
  • Lighting of moderate intensity is used depending on coral or clams types kept. Usually high powered fluorescent, medium size metal halide or LED.
  • Water quality demands start to go up. A protein skimmer is  typically used.
  • Tank size can be small to large
  • Cost can range from moderate to fairly high primarily depending on the size of the tank and the lighting system selected.

This is a ‘Moderate Demand’ system



Small Polyp Stony (SPS) and Clam tank

  • Primary inhabitants are SPS corals and high light requiring clams. Although soft corals and LPS may be kept also, these are usually minor components of the system.SPS Reef Tank
  • Macro algae (especially Caulerpa species) should typically be excluded, as it will become a nuisance. Halimeda is one of the few macro algaes that is acceptable in this type of tank.
  • Water flow requirements are high.Wavemaker capability is normally used to simulate reef crest conditions.
  • Lighting of highest intensity is used, usually either Metal Halide or the new high powered LED lighting that has recently been introduced.
  • Tank size tends to run on the larger side of the scale. This is mainly due to the fact that the higher cost of setup makes it more difficult to justify that cost on a small tank. Also, some items such as MH lighting tend to make more sense on larger tanks due to possible heating concerns, though the newer high power LED lighting has helped to address this concern making small SPS tanks more feasible.
  • Cost is high due to need for high intensity lighting and highly agitated water motion. Specimen cost can also be higher when dealing with SPS corals and clams, but this is not always true.
  • Water chemistry demands are high.  These corals and clams can consume a lot of calcium and other elements from the water.  Protein skimmers are usually deployed.  On larger tanks Calcium Reactors and other equipment is also usually deployed to help maintain acceptable water parameters.

This is a “High Demand” system and places the highest demands on maintaining water chemistry, budget and usually the hobbyists time.


Mixed tankMixed Reef Tank

I should mention that it is possible to mix and match these systems somewhat. An SPS and softie tank for instance is fairly common, although care has to be taken to ensure the inhabitants don’t start turf wars. It is also natural for some systems to evolve from one type toward another over time as the hobbyist gains experience and their interests change.  Some soft corals secrete compounds into the water that can be detrimental to the SPS corals.  For this reason, a few SPS corals in a mostly soft coral tank tend not to fair very well.

It is important to have a goal for what you want your reef tank to evolve into because the end goal will dictate your equipment and specimen selections going forward. Although it is normal to evolve your thinking as you progress in this hobby, you can save both money and frustration by taking as clear a path as possible at the onset.

One good way to do this is to find a tank on-line or in your local pet store or at a local hobbyist house that demonstrates what you want to achieve and use that as your basic model as you plan your requirements.