After many years of keeping aquarium fish, many fishkeepers still practice using aged water in their tanks.

THE ADVANTAGES OF AGED WATER – In the early days of local fishkeeping, the most convenient way of ridding our tap water of chlorine and getting it ready for use in our aquariums was to “age” it. Of course everyone knows that our tap water contains chlorine, which is lethal to our fish. To remove the chlorine, we collect water in a container or an aquarium and we let it sit or “age” for at least 24 hours. This basically removes the chlorine in the water, rendering it safe for aquarium use.

Using aged water has many advantages, the first of which is that the water is chlorine-free and safe for the fish. Second, water aged for a few days is more stable. Sometimes, water from the tap contains dissolved gasses that may affect water parameters. For one, carbon dioxide in the water may temporarily lower the pH since it can create carbonic acid. Thus, by aging your water, you may remove the carbon dioxide and stabilize the pH while the water is still in the reservoir and not in the main tank, which might cause pH fluctuation and is hazardous to fish.

The biggest disadvantage of aged water, on the other hand, is time. You will need at least 24 hours before you can use your aged water. Thus you can never have aged water available at once—unless, of course, you stock up on it. This is a very good practice and it may be worthwhile for you to consider setting up an adequately sized reservoir for your aquarium needs. With a reservoir, you will have aged water available for use at any time.

A reservoir is a container that will hold your water. Rather than just pulling out any container and filling this up with water, you might as well consider the following points I will present to you as you make your selection as to what is the best container for your needs.

THE BASICS – The most important point to consider for your reservoir is the size of your container. Considering we do a 40% water change a week (which is quite generous), and we age water for 3 days (which is more than the required 24 hours), then a reservoir capacity of 20% of your total tank volume should be adequate for a week.

To make this point clearer, let me cite this example. If you have two 50-gallon tanks, then your total tank volume is 100 gallons. My recommended size of container is 20% of 100 gallons, which is 20 gallons. With this, you are able to do a 40% water change in the first 50-gallon tank (which is equivalent to 20 gallons) using water aged from Monday to Wednesday. Likewise, you are able to do another 40% water change in the second 50-gallon tank (which is equivalent to 20 gallons) using water aged from Thursday to Saturday.

Better yet, the recommended 20-gallon reservoir will allow you to do a 20% water change using aged water on
both 50 gallon tanks, twice a week.

Air Stone.

If it still confuses you, let me assure you that a container that has a capacity of 20% of your total tank volume should be adequate enough for your needs if you refill this every 3 days.

Another important point to consider is the material of your container. Some materials can affect the pH and hardness of the water you have kept in storage. Cement ponds are an example of this; since cement is alkaline based, it will surely increase your water’s pH and hardness. This is bad if your fish require low pH with soft water, like dwarf cichlids, altum angelfish, etc. Conversely, however, for Tanganyikan and Malawi
cichlids, which prefer alkaline and hard water, this is a good thing.

It is best to opt for containers that do not alter water composition. Plastic bins and aquariums are great examples. These materials are inert and will not alter the water’s composition.

But just before you set up your reservoir, you might as well consider common tasks that revolve around the
facility. One such task is filling up the reservoir. This task shall be done once every 3 days, so it makes sense that the reservoir be situated near the source of water. Since this task will be done quite often, you don’t want this to be such a burden. Place the container near the water source, or better yet, have a water line to it installed. Another task is to move aged water from the reservoir to your tanks. Rather
than manually carrying bucketfuls of water to fill up your aquariums, you may elevate your reservoir and let gravity fill up the aquariums. Or you may use a submersible pump to move water from
the reservoir to the tanks; in which case, the reservoir should be situated next to a power outlet.

Power Heads.

Another very important reason for your reservoir to be near the power outlet is to provide strong aeration while aging water. Water kept stagnant in a container will be more harmful than
useful. If kept stagnant, you may still remove the harmful effects of chlorine but the low oxygen conditions may foster growth of anaerobic bacteria. This causes the water to smell foul, and it will have very low levels of dissolved oxygen; this may expose your fish to serious trouble.

Another serious concern associated with having a container filled with stagnant water is
mosquitoes. Mosquitoes lay their eggs in stagnant water because they can land on the water surface. Thus if the water in your reservoir is stagnant, you are providing them with the best conditions to multiply and invade your fish room. Worse, you may even put yourself and others at risk of getting infected with dengue.

Proper aeration is therefore a necessity. By using an air pump with an air stone, you are able to increase the dissolved oxygen in the water. With more oxygen, the growth of anaerobic bacteria is prevented. The bubbles created also allow other dissolved gasses to escape the water column. Thus, as mentioned earlier, aeration releases carbon dioxide, which enables you to stabilize your pH. Lastly, with strong
aeration, the constant moving of the water’s surface prevents mosquitoes from laying eggs. Thus, you also avoid the mosquito problem.

If you do not have an air pump, another option is to use a powerhead. But instead of the usual horizontal
position, I set the power head pointing up. This jets water directly to the surface and agitates the water more vigorously, thereby maximizing the oxygenation of your water.

Lastly, I recommend putting a light cover on your reservoir. This is not to seal it tight, but rather, just to make sure nothing falls into it while you are aging the water. We would like to keep dirt and other materials that could potentially contaminate the water out of the reservoir.

Having a reservoir for aging water is indeed a big advantage for the fishkeeper. It provides you with good, clean water very much suited for your fish. By addressing these key points highlighted above, you are able to provide enough aged water for your needs and as you need them.

This story appeared in Animal Scene’s July 2016 issue.