Freshwater Aquarium Chemistry by Blue Falcon
Freshwater Aquarium Chemistry
Water chemistry, or water quality, is quite possibly the single most important thing you need to know about in this hobby. We don’t really think of what comes out of our tap; to humans, it’s just water, but to fish it means everything. Think of it like the air we breathe. The 5 things every freshwater aquarist must test for are pH, water temperature, ammonia, nitrites and nitrates.
IMPORTANT!
If your tap water is provided by the city and comes from a water treatment facility, your water must be treated with a water conditioner to remove all amounts of chlorine, chloramines and heavy metals that are extremely dangerous to your aquarium inhabitants.
Always rinse your hands thoroughly before you place your hands in your tank. Cleaning chemicals could kill every living thing in your aquarium. This also includes soap, lotion and aerosol products.
pH (potential of Hydrogen)
pH is how acidic or basic (alkaline) your water is. In a tropical community aquarium, your target pH should be neutral at 7.0. Some fish may require slightly higher or lower. Depending on what your fish require, you can adjust your tap water accordingly using water buffers to either raise or lower the pH. Water buffers normally come in a bottle and are sold in powder form. Although providing your fish with the correct pH is important, your fish can be acclimated to live in a slightly lower or higher pH. Stability is more important than attempting to provide your fish with the perfect pH. For example, the pH of my tap water is 7.5. My fish would prefer it if my water was 7.0. To correct this I could add a buffer to lower my pH however my experience with buffers is not a positive one. An acid buffer basically converts the GH (general hardness) into CO2, which in turn makes your water more acidic. However once the CO2 is released out of the water through surface gas exchange, the pH bounces back up to its original value. This rollercoaster effect is harmful and often deadly to your fish. Instead of attempting to buffer my tap water, I slowly acclimate my fish to live in a slightly higher pH. Remember, stability is the key!
Let’s say however that your tap water is very hard and basic and you want to keep a fish that requires soft acidic water. You can lower the pH of your water without buffers and still maintain stability. To do this you simply dilute your tap water with RO (reverse osmosis) water until the correct softness and pH is achieved. (For more information about RO water, see the equipment section).
GH (general hardness) and KH (carbonate hardness)
GH is the amount of dissolved solids in the water which act as a natural buffer. For instance water with a low GH will be less stable and the pH may fluctuate more. A percentage of your general hardness with always include carbonate hardness, or the amount of carbonate in the water. In most cases you will not need to test for or worry about the GH of your water unless you are keeping delicate inhabitants or plants.
Oxygen
Although you may not associate oxygen with water, it is still extremely important for our fish. Fish use oxygen for respiration just like we do, and just like us they convert that oxygen into CO2. You can introduce oxygen into your aquarium water using an air pump hooked up to an air stone, but to be honest I was never really sold on these devices. As long as you have surface movement and disruption, oxygen will find its way into your aquarium water, just as CO2 will find its way out through surface gas exchange. Your filter should provide adequate surface movement to get the job done.
Temperature
The temperature of large bodies of water such as a lake or river is somewhat stable year round. However aquarists are constantly battling heat issues in such a confined system such as our aquarium at home. It is important we monitor and stabilize the temperature of our aquarium with the use of heaters and chillers. The target temperature for most tropical aquariums should be around 78ºF. You should research to find out what temperature each of your fish prefers before adding them to your aquarium. Some hardier fish can be acclimated to life in water a few degrees warmer or cooler than their natural habitat. Again, remember that stability is the key.
The Nitrogen Cycle
Failure to understand the nitrogen cycle is probably the leading cause of failure for all beginner aquarists. Adding too many fish into an aquarium too fast will result in “new tank syndrome”. If you have had an aquarium before where every fish you seem to add ends up dying, it is most likely because the tank was never properly cycled. Without knowledge of the nitrogen cycle, it is easy for a newcomer to get frustrated and give up in this hobby. You don’t have to be a chemist or biologist to understand the basics of the nitrogen cycle.
Toxic ammonia is introduced into to water through decomposing uneaten fish food, fish waste and through fish respiration. As ammonia levels rise, aerobic bacteria begins to colonize on our Aquarium Rocks, decor, substrate, and within our filter. This beneficial bacteria converts the ammonia into nitrites, which is slightly less toxic, and then another type of beneficial aerobic bacteria converts the nitrites into an even less toxic compound called nitrates. Nitrates are the end result in the nitrogen cycle and we must physically remove them through frequent water changes. Aerobic bacteria thrive in high oxygenated water, we just have to sit back and wait for them to go to work. It takes roughly 6 weeks from the time you first introduce an ammonia source into your aquarium for the nitrogen cycle to be complete and ready to be slowly stocked with fish.
The easiest and most humane way to cycle a tank is called a fishless cycle. What this means is we provide an ammonia source (such as adding a raw shrimp and allowing it to decay) and waiting for the nitrogen cycle to complete. During this time you should not perform any water changes or add any fish and you should be testing for ammonia, nitrites and nitrates every few days to give you an idea of which stage the cycle is in. When ammonia and nitrites fall to and remain at zero, you may now do a water change and slowly start stocking your tank. And please don’t forget to remove that raw shrimp. Some people also do what is called a natural cycle using a hardy fish that can tolerate high levels of ammonia and nitrites. Although I have done this in the past, I would suggest doing a fishless cycle so you don’t put any animal through the stress and discomfort of a cycling tank. There are a few ways to speed up the nitrogen cycle if you happen to be as impatient as I am. There are some commercially available products that add the bacteria to your tank, but I have never had much luck with these products. The method I use is transferring sand, rock or filter media from a mature, already cycled aquarium into my new aquarium. This will introduce beneficial bacteria and allow them to colonize more quickly.
Water changes
In nature, toxins and waste are diluted and filtered out over time. In our home aquarium however, it is our job to ensure our fish have the cleanest water possible. We do this with water changes. I would suggest changing 25% of your aquarium water every week to keep your fish happy and healthy. Conducting a water change is really not that difficult, so don’t get lazy and slack on it. Make one day a week water changing day. For me, I conduct water changes for all my tanks on Sunday so I won’t forget.
First, unplug your filter and heater. Next, siphon out 25% of your tanks water with a gravel vacuum into 5 gallon buckets. While siphoning, gently push the siphon into the substrate several times in different places to pick up any detritus, debris or uneaten fish food. If you have sand, you need to be careful not to siphon up the sand, so instead of pushing the vacuum into the sand, just lightly move the vacuum above the sand to pick up any debris. Once you have removed 25% of the water, remove your filter media from your filter, vigorously shake and squeeze your filter media off into the old tank water to clean them off, and place them back into your filter. This is what I do with my mechanical and biological filtration. If you have cartridges you may replace them at this time and any chemical media that needs to be replaced. You can now discard the old tank water and prepare your new water. Fill your 5 gallon buckets back up with the appropriate amount of tap water while adding the appropriate amount of water conditioner (if needed) at the same time, ensuring the conditioner is mixed in thoroughly. Try to match the tap water temperature to the temperature of your aquarium water while you fill your buckets up. With a cup or pitcher, gently pour the new water into your aquarium. Once it’s full, plug your heater and filter back in and you are done with your weekly water change. If you have well water, you may want to check out a product called the Aqueon water changer. It conveniently hooks up to your kitchen faucet to siphon and refill your aquarium to eliminate having to use buckets. The system advertises that you can use it with city tap water as well; you would just have to add the tap water conditioner directly to The Aquarium as its being filled back up. I’m not sure how I feel about using this product with city tap water since your fish will inevitable be exposed to some amounts of chlorine and chloramines while the tap water conditioner is working, so for those of you who have city water, use this product at your own risk.
Where can I find more information about aquariums?
Epic Aquarium is a site that teaches beginners how to set up an aquarium. Learn about types of aquariums, equipment, how to set up an aquarium, stocking fish, controlling algae and more!
About the Author
I am an aquarium enthusiast dedicated to teaching beginners starting out in this hobby. I am also the author and designer of EpicAquarium.com
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