Water Change: The 2hr Way

Introduction

While many hobbyists rely on ammonia/nitrite/nitrate water parameter readings to monitor their water quality, these parameters alone do not give a complete picture of water quality. The aquarium water may contain high levels of pathogenic bacteria (in the case of new/unstable/underfiltered systems) or other forms of organic waste molecules that have not yet broken down to more basic organic waste forms such as ammonia. This leads to the common scenario where hobbyists find that "oh my parameters are perfect, why did my fish die? Poor water quality will also lead to the melting of plants and poor growth form/colour in sensitive species. Breeders of rare and exotic fish will often change the water several times a week, even if there are no negative parameter readings, just to ensure that the water quality is high.

Ammonia/Nitrite/Nitrates in this tank are consistently 0 due to the combination of high plant mass and low fish loading. Why do we still bother with large weekly water changes?

Water changes not only remove dissolved organic waste, they also remove free-floating algae spores. It also allows you to re-balance water parameters that may have shifted during the week. While hobbyists may not have made significant changes to a planted aquarium over the course of a week, the aquarium ecosystem is self-evolving, growing and changing over time. Plants shed old leaves and excrete waste metabolites - both of which can trigger algae growth if not removed with water changes. This is particularly true in aquariums where high lighting levels are used to achieve stronger colouration and denser plant clumps. Low light aquariums have much less of a problem with organic waste. There is a strong correlation between the removal of organic waste and an algae free tank in higher light tanks.

Behind every pristine looking planted tank is a ton of expert maintenance, including the consistent removal of algae triggers - older leaves, organic waste both solid and dissolved.

Regular water changes are an easy way to rebalance the closed ecosystem of planted aquariums and keep the tank clean. It is best to do this weekly, changing between 30% and 70% of the water.

Can aquasoil get dirty?

The idea of a soil substrate getting dirty is an extremely strange concept for newer hobbyists - isn't soil just an accumulation of dirt? The organic waste that accumulates on the surface of Aquasoil is very different from the components that make up Aquasoil. This is better understood through the idea of composting - many gardeners compost their kitchen waste before adding it to their gardens. This creates a biologically stable medium compared to the overly labile conditions that would be created by adding raw kitchen waste directly to the garden soil. Similarly, aquasoil is made up of weathered organic matter and clay, which is much more biologically stable than the undigested organic waste that accumulates on the substrate surface over time.

Aquatic plants shed older leaves and these are broken down by shrimps and other detritivores. Bits of organic material and animal waste accumulate in the upper layers of the substrate. While the accumulation of organic waste on the Aquasoil substrate provides some nutrients, it does so at the expense of being a significant trigger for algae. It is much cleaner to remove the unstable organic waste layer and fertilise the tank with pure elemental salts - this results in fewer algae triggers.

This tank is about 2 years old when the picture was taken. Large regular water changes, with regular siphoning of substrate detritus, keeps it looking clean. This tank runs onAPT Complete and APT Jazz. A keen observer will notice how clean the aquasoil looks despite the age of the tank. This observation can be applied to most tanks with very high light levels - you will rarely see a pristine, algae-free tank with a very dirty substrate zone.

Water change the 2hr Way:

Water changes should not only focus on replacing the water in the tank - aquarists should also use this opportunity to remove detritus that has built up on the substrate layer.

This is done by hovering a siphon over the surface of the substrate while stirring up surface debris with a turkey baster. For weekly cleaning, do not aim to disturb more than the top layer of the substrate.

Video demonstration:

Cleanliness helps in growing difficult plant species

The link between tank cleanliness, water changes and plant growth is not immediately obvious to newer hobbyists. People tend to focus on nutrients, CO2 injection or light as plant growth factors. However, good maintenance plays a much bigger role than most people realise. By eliminating algae triggers in the tank, aquarists can use much more light and fertiliser without experiencing serious algae problems. Above 150 umols PAR, we get much more intense colouration and increased density of coloured plant foliage. This allows delicate, light-hungry plant species to reproduce more quickly.

Hygrophila sp Chai is a mutant plant created in a laboratory; it does not exist in the wild. It's difficult to grow and its older leaves are particularly susceptible to algae. To grow it well over the long term, attention must be paid to the cleanliness of the substrate. People fail to grow large clumps of it not because they do not provide enough light or nutrients - it is often because they do not keep the area clean enough for the plant to look immaculate.

Rotala tulunadensis is sensitive to the accumulation of organic waste in the substrate zone. If it is growing poorly, siphoning off accumulated organic detritus from the top few inches of substrate (while leaving intact aquasoil grains) will often solve the problem.

Tired of getting BBA on slower growers in your high light tank? Tank cleanliness is often the problem. The white Anubias above are grown in a high light tank - they would be covered in algae if the tank was not maintained consistently.

Hardscape heavy setups

Large, regular water changes remove algae triggers and allow for the flawless presentation of hardscaping where there is little plant mass to defend the tank against algae.

How does the sand stay white long term? Light control and water change the 2hr Way.

Situations where one should not do large water changes?

There are a few unique scenarios where large water changes should not be made. If the source water quality is extremely poor or unstable, smaller water changes should be made. In some areas with poor infrastructure, tap water may contain high levels of heavy metals, ammonia, or have high variability in alkalinity, etc. Regardless, any water drained from the tank should be used to siphon off excess detritus from the substrate surface.

If the quality of the tap water is poor, the use of an RO (Reverse Osmosis) unit to produce consistent, pure water will allow more predictable results in the aquarium.

High plant mass, low light, low fish load tanks

Tanks that have a large but slow growing plant mass, such as non CO2-injected tanks, produce much less organic debris than CO2-injected tanks. The faster growth rates of CO2-injected tanks lead to a much faster increase in plant mass, which leads to faster overcrowding and the abandonment of older leaves in less optimised positions in the tank, leading to a rapid increase in organic debris.

In a slow-growing, low-tech tank with high plant mass, especially one operating at lower light levels. The triggers for algae are suppressed to such an extent that such tanks can go much longer without water changes and still be relatively free of algae.

For people with very poor quality tap water, this type of tank may be the easiest to maintain in the long term, compared to high light high tech tanks which require more frequent water changes to maintain their stability.

Click here to read more on substrate maintenance.

Click here to read more about how much water to change for particular setups