Much thought should be given to the substrate. It is usually
the first item of hard decor to be added to a tank and arguably the most
difficult item to change once the aquarium is up and running. A substrate not
only makes the aquarium look complete but provides anchorage for plants, a home
for essential Nitrogen Cycle
bacteria and most importantly a natural environment for the fish.
The materials for a substrate come in many shapes, sizes and
colours and the first consideration should be for the needs of the fish. After
all it is their home you are furnishing. Some fish, such as cichlids and
loaches, like to dig or burrow in the substrate as part of their breeding or
feeding procedure. In these cases a fine smooth substrate should be provided so
that the fish may exhibit their natural behaviour. Avoid sharp gravel in any
case as this may harm mouths or barbels. Some aquarists section off areas and
use a variety of substrates. I like to partition an area of sand to allow
Corydoras sp. and other catfish to forage. Conversely, some fish
appreciate a substrate of small pebbles up to 1 in diameter to replicate fast
flowing river beds but, as large grain substrate collect wastes easily, these
material should be confined to aquaria with powerful fast flowing filtration
consistent with the environment one is attempting to recreate.
Not every type of gravel or sand is suitable for the aquarium.
Some gravels contain metals or are of a calcareous nature (i.e. contain lime).
While calcareous gravel is not harmful, it increases the
hardness of the water and may raise the
pH. Many fish do not like hard water and few
plants will tolerate it. On the other hand some products like coral sand are
desirable because of their calcareous nature. They act as a pH buffer, helping
to maintain an alkaline pH necessary for some fish, notably African Lake
Cichlids. Always research the needs of the fish and choose the substrate
accordingly. One can easily test the calcareous nature of gravel by adding a
few drops of vinegar to a sample of the substrate - if it fizzes it contains
lime. Testing sand for metals is just as easy. Place an algae magnet in a
plastic bag and pass it over a sample of sand. Any metals will be attracted to
the magnet! If you are unsure how safe a material is for your fish always ask
your local retailer or if in doubt, leave it out!.
Recommended substrate materials include:
- Silver sand (available from garden centres)
- Quartz gravel
- Volcanic ash
- Granite gravel
- River gravel (mixed grades of gravel look more
natural)
- Coral sand (for hard, alkaline water species only)
- Beach leaves (dry out and microwave for one minute before
use)
The colour of substrate is also important. In the wild, many
tropical aquarium fish live in areas where the bed is covered in thick mud or
leaf litter. A dark substrate therefore makes the fish feel secure and brings
out their natural colours and behaviour. Light coloured substrates create glare
and can cause fish to retreat or lighten in colour. It is worth noting though,
that in some cases no substrate at all is desirable for example in breeding
tanks for hygienic reasons, and in this instance the glass base itself can
cause glare. Breeders solve this by placing dark paper underneath the tank or
by painting the base of the tank.
When laying the substrate, unless an undergravel filter is present, I like to keep the
depth to a minimum. I have found that shallow substrates are easier to clean
and there is less chance of wastes compacting, clogging the substrate and
turning the useful aerobic bacteria (which grows on every surface in the
aquarium) anaerobic i.e. bad. With gravel, I usually lay the substrate around
½ inch deep. As for a sand substrate, I lay just enough to cover the
aquarium floor so that sifting or burrowing fish do not expose the base of the
tank. An undergravel filter requires 2-3 inches of gravel to be effective. Do
not use sand with an undergravel filter as it will clog. If laying a nutrient
base for plants, first lay a ½ inch deep of gravel substrate then the
nutrient base and finally cover with 1 inch of fine gravel. This prevents the
nutrient base from rising and being washed around the aquarium.
You may be thinking that with these minimal depths of
substrate how do I secure and grow plants? I like to terrace areas of my tank
with wood and rocks and plant in these areas. There are several advantages for
doing this. Terraces give the aquarium more visual depth and also help to
segregate and confine areas of differing substrates. They also prevent
carefully sculpted areas of the decor from leveling out. Planted areas can
therefore be created quite deep and remain undisturbed. I never clean my
planted terraces but allow nature to take its course in these areas.
Additionally, different grades of substrate can be used around the aquarium and
this creates a more interesting and aesthetically pleasing tank. Finally, I can
confine plant nutrients to the planted areas only, knowing that fish
(generally) won't disturb plants and spread the nutrient base around the
tank.
When using an undergravel filter, try to avoid large terraces
which may end up 6 or more inches deep. Instead, gently slope the substrate
from the back to the front and terrace only at the sides or around the uplift
pipes. This makes maintenance easier as dirt will accumulate at the lowest
point, the front of the tank where plants tend not to be growing yet still
allows water to be easily pulled through the substrate.
My last tip concerned with the substrate is always wash it
thoroughly before installation - even if the product claims that it is "ready
washed". This prevents problems such as cloudy water and clogging later on. Use
a bucket and rinse a small amount of gravel at a time gravel as if panning for
gold until the water runs clean.
Addendum: Many readers
have asked about the pros and cons of using sand in an aquarium. I hope this
table will help:
