What is the purpose of aquarium tank substrate?
You can have a tank without substrate, but having something in the base is much more natural. There are several reasons why your tanks should have a layer of substrate on the base.
For many, it offers a place for any waste or uneaten food particles to settle and become captured, until the time comes for them to be cleaned up. This prevents them from breaking down as much and making the water cloudy or full of ammonia.
Something like gravel also acts as a natural bacteria medium, encouraging the production and growth of ‘good’ bacteria which will help your tank filter out when cleaning the water. This bacteria can also help your plants to thrive, which boosts the life of your tank.
Some fish are benthic, so they naturally go along the bottom of the tank floor finding waste and food. Catfish and goby are two commonly found bottom-feeders in home aquariums.
Breeds such as jawfish like having a sandy surface to dig into and hide or ‘hunt’. This burrowing can help them to feel safe, and the substrate also doesn’t reflect the image of the other fish in the tank as glass does, so they can stay hidden.
Of course, the substrate can be aesthetic too. You can choose the colours, styles, sizes and material type if you want your tank to have a certain look, as long as your fish will be happy with it.
When combined with plants, hiding places, rocks and driftwood, it creates a natural mini ocean environment. A well-crafted aquarium also is said to have a positive health benefit on those who gaze at it.
How much substrate should I use?
It is a good idea to use an exact calculator to work out your precise amount based on the size of the tank, your fish and how many fish are in the tank.
Be aware that too much gravel or pebbles (with spaces in between) can cause too many anaerobic zones, which affect the chemical build of your tank.
How often will I need to replace aquarium substrate?
You can’t really change the gravel in your tank every year to alter the style and colour as you would paint your living room, change your curtains or get a new set of saucepans.
This is the environment of your fish, plus it is a lot of hard work to do this. Gravel helps act as a biological medium, for the promotion of healthy bacteria which in turn helps oxygenate the water and keep it all clean. When replacing this, you’d have to try and maintain this all which is difficult and requires a few days.
Vacuuming it and washing sections occasionally with a dedicated gravel cleaner should be enough to keep it clean. Purchase high-quality gravel and it should remain intact and looking good for years to come.
Which substrate can I use for plants?
Remember that the fish are your priority, but you do want something which works for both living things.
Soil is often best if you want to promote growth in plants, however, you may need something like gravel to weigh them down and be suitable for the fish to bury in. Gravel is great as it keeps the roots of the plant tight enough to stay put, unlike stones or pebbles.
Can I just use garden pebbles or gravel?
No! You must buy a substrate specifically used for fish, which is clean and neutral in pH. Don’t just go out to the garden and collect spare stones, or go to B&Q and buy what you’d use on a garden path. This could cause upset in the tank and dirty water.
Do I need to wash the substrate before putting it into the tank?
Most aquarium substrate for fish is prewashed (hence why you can’t just buy some from a hardware store). However, you may still want to prewash it as it can get dusty in transit. Small particles which can be separated may not settle in water.
You can place the substrate in a bucket and rinse by gently swirling, or put it in a sieve and rinse with a hose. You’ll never clean it completely, but once it has settled in the tank it shouldn’t cause too much upset to the water.
Can I buy coloured gravel for a fish tank?
It is readily available and could look great if you want an eyecatching display. However, just double-check the material of any coloured gravel before buying. Some are made from white dolomite, which is rich in calcium and magnesium and used to increase pH, alkalinity or water hardness.
If your fish don’t like this, or if your water is already struggling to be maintained, be aware.
Some people would argue that coloured gravel does not imitate a fish’s natural habitat and should be avoided, but fish are adaptable and there is nothing to prove it has a detrimental effect. However, we do have to say that a neutral coloured tank can a) make fish easier to spot and b) make the colours on fish really pop!