tank bottom choices

What goes on the bottom of your tank is one of those decisions you will make early in the process of setting up a reef or marine aquarium. Spend any time researching the various options in books and forums you will see that it comes down to basically 4 options and remember there are multiple ways of accomplishing a successful reef tank and the right way is the one that creates a stable system you are comfortable in maintaining and proud of.

Bare Bottom (BB)

Is what it sounds like – just the bare tank bottom. Reasons given for choosing this type include:

  • Easier to maintain and remove detritus from
  • Nutrient control is easier as there is no substrate for detritus to build up in.
  • You can create the higher flow rates some species prefer without sand being blown about.
  • There is some evidence that having no sand disrupts the ick life cycle

Reasons usually cited as cons:

  • Aesthetically it doesn’t look natural and any detritus is a distraction. A note to this is that over time will become covered by coralline algae and can be home to some corals and zoas. Also there are options for creating a faux sand bottom: starboard, painting the outside of the glass, and others DIY options.
  • there are species of invertebrates and fish (wrasse, goby) that require a sandy home.
  • Can be more difficult for rocks to stay put and falling rocks could break the tank bottom
Crushed Coral (CC)

Different materials are sold as crushed coral but are primarily crushed limestone from ancient reef areas and can be primary calcite, aragonite or a mix that are then graded to a grain size (2-6mm) for marine aquariums. Reasons given for choosing this type include:

  • Looks better than a bare bottom.
  • Long lasting
  • A substrate for top of an under-gravel filter (fresh systems mostly)

Reasons usually cited as cons:

  • Becomes a detritus trap and needs constant cleaning. A common counter to this: Can be negated by a maintenance schedule of vacuuming and water changes.
  • Conducive to becoming a nutrient sink and harboring nitrates.
  • Less favorable to worms and other sand dwelling organisms. Crabs and snails can have difficulty maneuvering through it. Can cause obstructions in fish who suck and spit substrate and can physically harm some who dive or burrow into it.
Shallow Sand Bed (SSB)

Are somewhere between 1 and 3″ deep depending on who you read / talk with. They can be made from various sand types, sources, and grain sizes. Reasons given for choosing this type include:

  • Are more natural in appearance in more what we expect a seafloor to look like.
  • Can keep a wider variety of fish, including those who like / need sandy areas.
  • Provides another surface for microfauna filtration organisms
  • Less to keep clean compared to deeps sand beds
  • More viewing area compared to deep sand beds

Reasons usually cited as cons:

  • High flow rates can create sandstorms and relocate sand.
  • Can become a source of debris and nuisance products if not maintained.
Deep Sand Bed (DSB)

Are somewhere between 3 and 6+” deep depending on who you read / talk with. They can be made from various sand types, sources, and grain sizes. Reasons given for choosing this type include:

  • Properly set up they develop zones that allow for various biological processes to occur that are beneficial to controlling system parameters like nitrite, nitrate, and deeper zones harbor denitrifying bacteria that convert nitrate into nitrogen. (see Deep Sand Beds, R. Shimek: Pro’s and how they work)
  • Provides homes to a wide range of micro-fauna, invertebrates, and fish.
  • Provides better filtration

Reasons usually cited as cons:

  • Can become a storehouse for toxins and nutrients that may become a “ticking time bomb.”
  • Removing or replacing can be a logistically challenging and dangerous to the system’s inhabitants.
  • Require periodic re-population of the microfauna to keep it from compacting.
  • Have a limited life span
Other Helpful Links:

Sand Calculator: How much sand you will need based on your tank lenght, width, and desired sand bed depth

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