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• HOW TO - Aquarium Water Changes

16 February 2023

An aquarium needs regular maintenance to stay in top condition. Freshwater lakes are open systems, usually having a fresh supply of water feeding in and a site where it drains to. They are also affected by environment changes, such as evaporation and rainfall. Fish tanks are closed systems - they have no access to loss of water and replenishment. If the aquarium has a lid, evaporation is also kept to a minimum. Water changes are therefore an important part of regular aquarium maintenance. Water changes emulate the replenishment of water fish and plants would get in a wild open system.

Partially changing the aquarium water has many benefits. It removes the build up of waste products, such as nitrates and phosphates. Fresh water helps replenish essential carbonates and minerals used from the water. Remineralisation help stabilise the pH (and KH) value of the aquarium. For planted aquariums it offers a ‘reset’ of plant foods and fertilisers. Below we explain why water changes are important, how often they should be performed and what products are recommended.

How often should I water change?
This is usually the first question asked by a new fishkeeper and the simple answer is, there is no right one answer! Every hobbyist will develop their own routine that works best for them and their aquarium. There is a good recommended amount that hobbyists can base their own routine on though. General advise is to perform:

• 10 percent of the aquarium water once per week.
• 25 percent of the aquarium water once every two weeks.

This gives the fish keeper the option of a couple of schedules. If the water changes are performed every two weeks, then the amount of water changed is more than if it were weekly. This is also just a starting guide - many fishkeepers (particularly those with heavily stocked tanks) will change more than this. Generally the maximum amount of water that should be changed at once should not exceed half. Changing too much at once risks impacting the filter bacteria. It can also be too much of a change in temperature and pH.

How do I perform a water change?
Carrying out a water change usually involves more than just removing and replacing water. It is the ideal time to perform other maintenance duties like cleaning the substrate and filter media. Unless your aquarium is situated on the ground, the easiest way to remove water is to syphon it. This relies on gravity to allow the flow of water without the use of a pump. Gravel cleaners are a very handy piece of equipment. They are made from a large diameter tube connected to a longer, smaller tube. The syphon is started and the large side of the cleaner is pushed in to the substrate. This lifts and removes detritus that has accumulated in the substrate (uneaten food, fish waste, dead plant leaves etc). This waste is then syphoned out along with the water whilst the substrate remains in place. Gravel cleaners can even be used on fine substrates (sand) but be careful not to suck up the substrate along with the waste!

Recently there has also been the introduction of motorised gravel cleaners. These have a small pump inside which prevents the need to start the syphon manually. They sometimes also have the ability to recycle the water in the aquarium through a fine filter pad. This allows the substrate to be cleaned without removing water at all (handy for mid-week cleans).

Gravel cleaners tend not to be used in densely planted aquariums as the disturbance to roots can cause damage to the plants. Marine substrates are often left undisturbed or only the very top layer cleaned. Disturbing the deeper layers can release a build up of nitrates and phosphates. Unless the aquarium is very large, the removed water is drained in to a bucket. This waste water is the perfect water to use for cleaning the aquarium filter. The process of cleaning foams in aquarium water means the trapped dirt is removed without affecting the beneficial bacteria. Rinsing filters with tap water can kill off the good bacteria, effectively resetting the aquarium cycle. The old aquarium water still isn’t done yet either! Dirty aquarium water is absolutely perfect to use in the garden, plants love it!

Essential products
Once the aquarium is ready to be refilled, fresh water needs to be conditioned before being added to the tank. Tap water contains chlorine and/or chloramine to kill disease-causing waterborne bacteria (cholera, typhoid, dysentery for example). The lack of these bacteria species is great when it comes to a safe drinking water supply. Unfortunately, it is not good for aquariums. Chlorine and other heavy metals are toxic to fish and kill the good bacteria growing inside the filter. It is very important to treat all new water before it is added to the aquarium. NT Labs Aquarium - Tap Water Safe safety and immediately removes chlorines, chloramines and other heavy metals from tap water. It also has an anti-stress additive to help reduce stress to fish during transportation and relocation.

If cleaning the aquarium filter when water changing, it is recommended to add a single dose of NT Labs Aquarium - Filter Starter. The friendly bacteria helps re-establish the biological filtration, helping to prevent any water quality issues post clean.

In planted aquariums, changing water ‘resets’ the concentration of plant fertilisers and additives. With NT Labs Aquarium CO2 Boost for example, the dose rate is doubled to 2 pumps per 25L when dosing on a water change day. This is to bring concentrations back up to recommended
levels for optimum plant growth.

Lastly, If the aquarium is cloudy after water changing, NT Labs Aquarium - Liquid Filter can safely be dosed to rapidly clear the water. The microparticles act as magnets to bind particles together, leaving water crystal clear. Other benefits of liquid filter include binding heavy metals
(much like dechlorinator) and remineralisation of the aquarium water.

A Few More Hints & Tips

• The olden days of simply leaving water ‘to stand’ for 24 hours to remove chlorine doesn’t apply anymore. The addition of chloramine in tap water was designed to prevent dissipation of chlorine (as naturally it presents as a gas). Chloramine is much more stable in water and will not disappear without an additive such as Tap Water Safe. The only benefit to letting water ‘stand' is to get it to room temperature without using a spare heater.
• Be careful on the percentage of water being changed. Never change more than 50% at once. In winter even more than 30% without pre-heating the new water can be too stressful for tropical fish.
• In larger aquariums, changing water bucket by bucket can be a labour of love! Consider an extended syphon tube and re-filling the aquarium directly from the hosepipe. If doing this, add enough tap water safe to dechlorinate the entire aquarium volume (not just what is being added). Add this to the aquarium before refilling!
• Test the pH levels of the aquarium and your fresh tap water. Try and keep the pH values similar to prevent shocking the aquarium. NT Labs Aquarium - Narrow pH Test is highly accurate within the most commonly seen pH values of aquarium and tap water (pH 6.0 - 7.6).
• For marine aquarium water changes, you must only change as much water as you have prepared to refill. The easiest way to achieve this is to have the same container size as the one where the new saltwater is being mixed. Drain the aquarium in the spare container so as to not take out too much. This is to help keep a consistent salinity range and to prevent dilution from an auto top off or running out of prepared salt water!
• Also for saltwater, make sure the salinity is the same (usually 1.026SG / 35ppt for reef tanks) in the aquarium and the new salt water. Coral and other reef invertebrates will not tolerate salinity fluctuations very well.

Tagged in: Indoor