A very important area that may often be overlooked is the makeup of the tanks substratum.
Substratum is the material used to cover the bottom of the tank.
In many cases this material is chosen only by deciding how it will appear in the tank.
Color and size being the main criteria.
This can produce harmful effects in your tank.
Much more consideration needs to be given.
First of all the chemical makeup of the substratum needs to be decided.
Some of these materials will lower the pH of the water which affects the waters alkalinity.
Also because some fish and other marine creatures enjoy burrowing through the substratum, material with rounded corners and not sharp corners should be chosen to avoid your tanks occupants.
If your tank utilizes an under bed filter, in other words a filter that is located under the substratum, then you should have at least 3" of substratum material.
An alternative method is to use sheet of synthetic sponge about and inch thick.
This in turn is covered with a layer of egg crate diffuser grating.
On top of this is placed just one inch of the chosen substratum material.
this system while a little more trouble to install will lower the weight that the heaver grave or substratum would normally add.
Most aquarium owners agree that one of the best bedding materials is Philippine coral gravel.
It's particles are mostly uniform in size which eliminates the problem of clogging the bottom filter.
Although usually the most expensive it will make up for it's cost by providing less maintenance and a healthier environment for your fish.
Some of the other materials that will work well are course quartz gravel, crushed dolomite, crushed oyster shell and crushed coral.
Be sure to check with a good authority regarding the proper method to use each of these materials.
As with anything you chose to add to your tank clean it thoroughly by holding it under running water.
You need to remove any existing organic mater which may be mixed or adhered to the gravel.
Smelling the material will often times reveal the presence of decaying organic matter through it's foul odor.
Hopefully this information will get you started in the right direction to chose the proper substratum for your tank.
As usual do your research, find what is available and try not to let price be the major factor in your decision.
A material that costs a little more may save you many dollars spent in correcting a problem later on.