The Chemistry of Tank Decor
By Ashleigh
Copyright 2007

This is a subject that has interested me for some time and I have been wanting to write an article about this.  First, however, I feel the need to gather more information from others about their experiences and knowledge on this topic.  I can illustrate what I have come to understand from my own experiences and research.  

I strive to decorate my tanks for more than just looks.  I want to achieve the most suitable atmosphere for the fish that I choose to keep based on their natural environments, as well as affecting the water chemistry to be appropriate for their needs, and still have it look good.  I will demonstrate my personal conclusions in a comparison of two of my tanks that are on opposite ends on the scale of water chemistry and I will compare them both to my tap water.  Then we will discuss how we reached such different results on the chemistry scale.

African Cichlid Tank
The decor that I have chosen to use that naturally raises the PH, KH, and Alkalinity include Dolomite sand which is very high in calcium content, hence the high KH which in turn affects the pH, an assortment of sea shells which are also made of calcium and slowly releases carbonates into the water as they dissolve over time, limestone and marble, a small portion of African Rift Lake Salts added during water changes that are not actually salts at all but are mainly a combination of calcium and magnesium with some other trace minerals.  This PH, KH, and Alkalinity is suitable for these fish and is achieved by the decor that I use with the exception of the Rift Lake Salts which I have been slowly weaning them off of since I converted their tank from plastic plants and decor to all natural substances.  I believe I can cut out the Rift Lake salts completely and still maintain an appropriate PH, KH, and Alkalinity.  

Freshwater Planted Community
This tank is pretty heavily planted and well stocked with a variety of different tetras, gouramis, botias, assorted catfish, and many Malaysian needlepoint snails.  I inject CO2 into this tank at approximately one bubble unit per 4 seconds, and I light it with a double compact fluorescent.  The PH is drastically lower as is the alkalinity and KH due to all of the live plants that are consuming carbon dioxide during the day, and releasing it at night which utilizes the hydrogen creating a PH lowering, acidifying, and water softening result.  For a more detailed explanation see the topic Water Chemistry.  

Also I have a large piece of bogwood in this tank which lowers the PH as well and has an acidifying, softening effect on the water, in other words creating a natural buffer.

The following lists demonstrate some non-inert substances for affecting the chemistry of your tank on two opposite sides of the water parameter scale.

PH Lowering/Water Softening/Acid Buffer Substances and Decor
Live Plants
Bog Wood
Mopane
Drift Wood
Peat Moss

PH Buffering/KH and Alkalinity Raising Substances and Decor
Dolomite, Calcite, Aragonite sands
Crushed Coral
Sea Shells (slowly over time)
Ocean Rock
Limestone
Marble
Tufa Rock

All of these substances affect the water parameters by simply placing them in the tank, however, other techniques may be used as well such as putting crushed coral or reversely peat moss into your filter unit to affect the H/KH/Alkalinity/Hardness in the filtration process, or you may soak these substances in buckets with the new water that will be added to the tank during water changes. 

 I, myself, prefer to utilize these substances as attractive displays in my tanks that will have the combined effects of ideal conditions for the fish such as building caves with pH raising rocks for example for territorial cave dwelling fish such as African Cichlids, as well as nice substrates that are suitable for the fish and nice to look at like black calcite, white dolomite sands, or crushed coral for example.  

Bogwood and Mopane woods make very nice centerpieces and accents in a tank as well as add to a great environment for tropical fish with low PH/KH and soft acidic water requirements such as many tetras, discus, angelfish, botias, SA cichlids and more.  This also provides an ideal range for aquatic plants to thrive in and to participate in the natural balance of water parameters in the tank.

The point that I am wanting to make with all of this is that it is quite possible to multitask the purposes of your tank decor to benefit a range of elements in providing the most suitable environment for you fish, as well as a naturally beautiful aquatic display.