Sand Options

There are many choices when dealing with substrate selection.  Not all of them are practical though you will still find them being used from time to time. Of the less desirable substrates are crushed coral, silicate-based sands, and crushed oyster shell. Ideally, aragonite sand and/or live sand is idea.  Many aquarists go with a combination of the two.

Aragonite sand is calcium based and slowly dissolves releasing calcium into the water-column which helps to maintain calcium levels as well as pH.  Aragonite sand may also release beneficial levels of other elements as well.

Aragonite is formed from naturally occurring biogenic (life-formed) minerals that reach equilibrium with seawater at a pH of 8.2. It also automatically dissolves into its primary components of calcium, carbonate, and strontium when the pH falls below 8.2 (the natural pH of seawater) thereby driving the pH back towards 8.2 with a slight excess of strontium ions. However, adding excess calcium in any form can cause the solution to precipitate out of solution which can negatively effect aragonite substrate. (Extremely high calcium levels can cause binding of aragonite sand which can lower its efficiency)

Live sand has the benefit of bringing beneficial micro-organisms into the system to help maintain the sand-bed, though aragonite sand can just as easily be seeded with a few cups of live sand which would eventually result in the same benefit.

How Deep?

After selecting what substrate will be used, we must decide on how deep a sand bed we will need.  If you have already decided on an in-tank plenum, your answer is 4-inches. No more, no less.  However, if you have decided to go without a plenum, you choices of how deep are a little more open to you.  Many aquarists have successfully maintained a deep sand bed though some reports of hydrogen sulfide or hair algae outbreaks have been reported.

Many aquarists have gone with a thin 1-inch or less sand bed or no substrate at all, though most feel that a system without at least a little substrate on its bottom looks rather unnatural. This is probably an area that you will want to research further. I could give you my personal opinion but I don't want to influence you too much. Talk to other aquarists an decide what you feel is the safest method and one that you can maintain. If you do decide to go with a plenum make sure it has a four-inch sand bed. (probably only for larger systems due to the 4-inch depth of the sand bed which can look quite ridiculous in smaller systems.) Then again, some aquarists run plenums in auxillary tanks connected to the main system. This method is gaining popularity world-wide and may be the way of the future.

Selecting Rock