Water quality – not water clarity.

Water quality - not clarity

At Tetra, our customers often ask what it is that they should be looking for when it comes to pond and aquarium water quality. Many believe that it’s the clarity of the water that reflects its quality, however, this is not always the case. In fact, water clarity has very little to do with the actual quality of the water. For instance, many fish, such as goldfish or Koi, are renowned for preferring the security offered by murky water.

So, what should we be looking for when discussing overall pond or aquarium water quality? What are the signs of poor water quality? What are the problems with murky water and the problems with perfectly clear water?

What is water quality?

We can define this incredibly important concept as a description of the physical and chemical properties of the water. In other words, the profile of the water and the level of pollutants in it. For example, the water we draw out of the tap at Tetra’s UK offices is very hard and slightly alkaline. This hardness comes from the chalky rocks in our area dissolving minerals into the rainwater. This rainwater seeps down into the ground, is then extracted to be treated and turned into tap water. These minerals give the water a characteristic hard-alkaline profile.

So, water quality involves a description of the water’s profile, hard and alkaline, soft and acidic etc. These are chemical properties, but the definition also includes physical properties of the water, most notably temperature. Different fishes have varying environmental requirements of water and so good water quality for one species could be dreadful for another.

Water quality will change over time as living organisms extract and deposit various elements and compounds into it. Therefore, water quality also encompasses a description of the natural and unnatural ‘pollutants’ in the water. Natural pollutants could include ammonia, nitrite, nitrate, phosphate etc, all compounds released from natural processes in the pond or aquarium such as fish metabolism. Unnatural pollutants could include those substances added by man such as chlorine in tap water or other nasties such as heavy metals or pesticides.

The dangers of crystal clear water.

The thing to realise when discussing water quality for any fish is that the eyes are not chemical test kits. Two water samples, one of which was perfect for fishkeeping, the other which for example, had an incorrect pH (Acidity level) or too much ammonia or nitrite (toxic fish wastes), would look identical to our eyes.

We use chemical test kits to determine the quality and measure the properties of the water, such as pH, hardness and oxygen level and also the ‘pollutants’ such as ammonia or chlorine. There is no substitute for regular water chemistry testing.

Water chemical testing kits and test strips, such as those in the TetraTest range, are the only way to measure and determine overall water quality. Now with the Tetra Aquatics App, testing water and storing the results for comparison over time is a simple task. The common phrase ‘look after the water and the fish can look after themselves’ is as true as ever and our ability to monitor the water quality is easier than ever before.

Signs of water quality problems:

As we have seen ‘good’ fishkeeping water quality can look to us the same as ‘bad’ fishkeeping water quality, in the sense of the appearance of the water itself. However, the behaviour and physiology of the fish themselves can tell us much about the quality of their medium.

The most common example is the behaviour of fish in water of low dissolved oxygen (DO). When the DO level drops below that preferred by a fish they begin to ventilate their gills at a faster and deeper rate, and frequently move up to the water surface where the DO level should be marginally higher. This gasping at the surface is a behavioural and physiological response allowing the fish to extract enough oxygen for its needs, rather like us humans huffing and puffing when we are ‘out-of-breath’.

Many tropical freshwater fish have evolved organs to allow them to breathe air, and they will begin to use this special ability if the dissolved oxygen level of the tank begins to drop. An ideal example of this is Corydoras sp. catfish which dart up to the water surface to take a quick gulp of air if the DO level in the tank is slightly too low. The gulp of air is then swallowed where a highly vascularised area of the gut allows the uptake of oxygen into the blood.

However, a fish gasping at the water surface is by no means a unique sign of low DO levels. Many other parameters and pollutants can lead to gill damage which hinders the fishes’ ability to uptake oxygen leading them to gasp, even though the DO level is adequate for healthy fish.

Other ‘signs’ of poor water quality include the dreaded algae or blanket weed, which is an indication of an excess of plant nutrients in the system, most notably nitrates or phosphates. This can be prevented by using products such as Tetra PhosphateMinus which reduces high phosphate values to prevent the growth of undesired plants. Another good example is foaming on the water surface – this can indicate an excess of organic material in the system probably due to overstocking with fish or overfeeding. It is also a sign of under-performance by the filter system again due to too much fish or food, or due to some trauma to the biofilter.

So clear water does not mean good water quality, and murky water does not mean bad water quality. Why do we desire such clean water for our fish and why do we associate clarity with quality?

Why do we want clear water?

Firstly, we need clean water to ensure that we are creating an optimal habitat for the fish, but we want clear water for the simple reason that we want to see our fish. But is clear water good for them – would the fish choose clear water? I suspect not, as many fish such as goldfish or carp naturally prefer the cover offered by murky water as it hides them from predators. Common carp show better growth rates in murky water than clear. So, for our Koi to feel ‘comfortable’ in the clear water a refuge offering shelter and security will always be a welcome addition to a pond. This can often take the form of a bridge or deck by the pond which enhances the overall appeal for you and the fish.

Many fish such as catfish have superb senses of taste, smell and touch to find food, but their eyes offer very feeble vision – as the water they live in is so cloudy! The knifefish and the elephant-noses have adapted means of navigating through murky water and locating food through the use of electric fields emitted from their body.

So, is murky water all that bad? It depends on the source of the reduction in clarity. Murkiness due to mineral particles, such as clays, causes no real problems and mimics the natural environment of the fish. However, murkiness due to green algae turning the water into a pea soup is a different matter.

Firstly, the pea soup pond is not a pleasing feature in any garden. Secondly, a small amount of algae causes no problems for the fish, however if the algae population blooms and the pond becomes choked with growth then serious water quality implications follow. Excessive algal growth can cause wild daily fluctuations in DO, carbon dioxide and possibly pH levels in the pond, which has serious consequences on the health of the fish. The good news is that there is a range of liquid additives on the market which can be very effective at targeting both floating and pond algae, such as Tetra’s Pond AlgoRem, which provides effective and safe treatment for persistent blooms.

Ultimately, we all have our own preferences for water clarity for the fish. Some choose to have a slight cloudiness in the water for the fish to feel at ease. With the filtration technology available today it is possible to maintain terrifically clear water and provide aesthetically pleasing refuges for the fish. What we have no choice over is water quality, the fish have their set preferences dictated by evolution and we owe it to them to check the water always stays within their boundaries.