Freshwater Tank Basics
Introduction to Freshwater Fishkeeping
Starting your first fish tank can be exciting and nerve racking at the same time, especially for first time owners. No tank or tank owner is perfect at the beginning, and over time you will learn what to do and not do, which equipment and products work best, and which aquatic animals you love the most. If done properly, freshwater aquariums can be the most beautiful and rewarding addition to your home.
Choosing the Perfect Tank
When choosing the perfect freshwater tank, it’s important to start with your end goal in mind. There are a few common types of freshwater setups: community tanks, species-only tanks, and planted tanks. A community tank is one of the most popular options—it involves keeping a variety of fish species that are peaceful and compatible with one another. This allows for a colorful and active display, but you’ll need to research which species can live together harmoniously. A species-only tank, on the other hand, focuses on just one type of fish. This is common for fish that are either territorial or have specific care needs, such as bettas, cichlids, or goldfish. These tanks can be very rewarding, as you get to observe more natural behavior, but they require a bit more planning around tank size and filtration depending on the species. A planted tank is another beautiful option—these setups include live aquatic plants alongside fish. They’re great for those who want a more natural, self-sustaining environment. Planted tanks can range from low-tech (low light, no added COâ‚‚) to high-tech setups that require special lighting and fertilizers. The benefit here is that the plants help maintain water quality and provide hiding places for fish. Once you decide what type of tank setup you're going for, it’s time to choose what kind of fish you'll keep and how many. This will directly affect the size of the tank you’ll need. A good general rule for freshwater fish is “1 inch of fully grown fish per gallon of water.” This isn’t a strict law—some fish are taller, messier, or more active than others, so always do your homework and use your best judgment. Filtration, tank dimensions, and swimming space all factor into a healthy tank. Also, don’t fall into the trap of picking your dream fish before you’ve considered your space. If you don’t have room for a tank that can comfortably house that species at full size, it’s better to wait. Responsible fishkeeping means creating the right environment for the life you’re caring for. One last thing to consider: tank size matters, especially for beginners. Smaller tanks may seem easier to manage, but their water parameters can fluctuate rapidly, making it harder to maintain a stable environment. I personally recommend starting with at least a 20-gallon tank, as it gives you more flexibility and a larger margin for error. For aesthetics, there are two styles of tanks to choose from: rimmed and rimless. Rimless tanks offer a sleek, modern look with an uninterrupted view of your aquascape, while rimmed tanks have black framing that provides extra structural support and is typically more affordable. Both have their charm—pick what suits your taste and budget!
Essential Equipment
Freshwater equipment might seem a little less intimidating than saltwater setups—but there are still some key items you’ll need to create a healthy, thriving environment. In this guide, I’ll cover the essential equipment and a few recommended extras for freshwater tanks, including filtration, heating, lighting, cleaning tools, and chemical additives. Let’s start with water quality, which is the most important part of any freshwater setup. While you don’t need to mix reef salt like in saltwater aquariums, you do need to condition your tap water before adding it to your tank. Tap water often contains chlorine, chloramine, and heavy metals, which are harmful to fish. A water conditioner like Seachem Prime works instantly and is widely trusted in the hobby. If you want to take things a step further, you can install an RODI (Reverse Osmosis Deionization) system at home. It’s not necessary for most freshwater setups, but it can help if you have particularly hard or contaminated tap water. Even if you’re using RODI water or a conditioner, it’s still smart to have a water testing kit on hand. A good kit will let you monitor ammonia, nitrite, nitrate, pH, and hardness levels. I personally like the API Freshwater Master Test Kit—it’s easy to use and lasts a long time. When it comes to filtration, there are several great options depending on your tank size and stocking. The main types of filters are sponge filters, HOB (hang-on-back) filters, canister filters, and internal filters. Each has its benefits. For small tanks, sponge filters work great and double as gentle aerators. For medium-sized setups, I like the AquaClear Fluval Power Filter—it’s reliable, customizable, and easy to clean. Canister filters are excellent for large or heavily stocked tanks since they offer powerful, multi-stage filtration. I also recommend adding an air pump or powerhead if your filter isn’t circulating the water well enough—oxygenation is key for your fish and beneficial bacteria. Heaters are another must-have, especially if you're keeping tropical species. Most tropical freshwater fish do best in water that stays between 74°F and 80°F. I use the Aqueon Preset Aquarium Heater in a few of my smaller tanks—it’s affordable and consistent. For larger tanks, you may need two heaters placed on opposite sides for even heat distribution. Be sure to get a thermometer so you can monitor your tank's temperature accurately. Lighting depends on your setup. If you're keeping a basic tank with artificial plants or decorations, a simple LED light will do. If you're going for a planted tank, you’ll need a stronger full-spectrum light to support plant growth. Look for something with customizable intensity and a timer—your plants (and fish) will appreciate the regular light schedule.
A lid is also highly recommended. Some freshwater fish, like hatchetfish and certain barbs, are known jumpers. Even if your fish aren't known for jumping, a lid helps reduce evaporation, keeps out pet hair and dust, and prevents anything from accidentally falling in. Make sure to get one that fits your tank size—it’ll usually be labeled clearly.
Cycling and Water Chemistry
Once you have your tank set up and running you will be excited and ready to see your tank explode with life, but have patience! Your tank must have time to grow the necessary beneficial bacteria your fish and other creatures will need to survive. This is called cycling and it, like many other parts of tank setup, depends on the size of your tank and can take anywhere from a week to several months. The process is as follows: you feed, ammonia (waste) is produced, then bacteria and plants absorb the waste to make the water safer, ultimately preparing your tanks ecosystem to process ammonia. In simple terms, this is a natural method of filtration carried out by microorganisms and plants. Plants, in fact, are a better method of biological filtration than microorganisms in many cases. A study done on disease control in aquaculture actually found that plants stimulate the immune system of fish, help them avoid stress, and act as antibacterial and antiparasitic agents. So, how do you start the cycle? Once your tank is set up, all you must do is ensure your filter(s) is running, sprinkle a little bit of food to kickstart the bacteria growth, and wait while feeding every once in a while. All this to say, if this process is rushed or skipped entirely, there is a strong possibility that your fish will not survive. You can use the recommended time frame estimate for your size tank to determine when the cycling is complete, or another easy way to tell is when your plants start showing new growth! You will want to test your water using a water testing kit, as mentioned above, before adding any life just to be safe. An ideal reading would be 0 parts per million (ppm) on every test. Any changes needing to be made can be through a simple water change, or specific supplemental chemicals found at your nearest pet store. Your local pet store may also offer free water testing!
Selecting Fish and Compatibility
Choosing which type of fish you will stock your tank with is a fun and thought consuming process. There are so many different species of fish with different looks, habits, and personalities that you can come to love just like a regular house pet. However, not all species are compatible. It is important to research any and all types of fish you plan on having before purchasing to reduce the chances of damage or death in your tank. Consider the sizes of the fish when fully grown, how territorial they are, how aggressive they are, and their eating habits, breeding habits, and "nesting" habits. For a beginner, following the noted behaviors of certain species is recommended, but you will sometimes find that a species labeled as incompatible with another may live harmoniously. Another thing to consider when selecting fish is how your cleaning processes will go. This may also be a reason to look back on the section about selecting a tank. It is not uncommon to find that when removed from their tank and separated fish of the same and differing species may not get along when they are returned. When purchasing multiple fish think about what secondary location they will be placed in for cleanings and, if separated, if you are willing to accept the potential consequences that come with that action. A simple internet search or call to your local pet store can provide you with reliable information on multiple-species tanks, but below I have included a scientific website where you can search for any documented fish species and relevant facts about them:
Feeding and Nutrition
Saltwater and freshwater fish alike survive off of a number of different types of food. There are liquid foods, frozen foods, pellets, flakes, small live animals and bugs, and other fish. Typically, one type of food can work for all of the fish in your tank if they are around the same size. Sometimes fish are picky which will result in you having to either change the type of food you are giving them, or the method by which you feed them, but I personally would not recommend going out o f your way to do this unless necessary. I would recommend having a schedule that you feed your fish on (ex. once in the morning, once at night) to prevent over and underfeeding your pets.
Long Term Maintenance
Now that we have covered all of the necessary components of fish tank setup, let's talk about maintenance. Water changes are the most important thing to do to reduce ammonia and nitrogen spikes. The general recommendation is a two-thirds water change every two to four weeks. Too much new water can shock your fish and cause them to die, which is why you cannot completely empty out your tank. It would rid the tank of any beneficial bacteria, meaning you would need to restart your nitrogen cycle. A few cleaning tools I could not live without are a siphon (gravel vacuum), algae scraper, 5-gallon paint buckets (to drain old water), long plant tweezers, fish safe glass spray, a net, plant scissors, and a magic eraser (great for wiping down insides of tanks because they do not have chemicals)! Your filter(s) also need to be cleaned and have the media changed out, but not as regularly (maybe once a month).