Freshwater Aquaria (2021 FAQ Part 1): Before You Start


This FAQ contains a comprehensive beginners guide that covers all aspects of aquarium keeping, with a focus on freshwater aquaria. However, much of the information is also relevant to saltwater setups.

Before you start – what you should know before setting up your first aquarium?

What is involved in keeping an aquarium?

As far as pets go, fish are a relatively low maintenance and low cost option, provided that their aquarium is properly set up. Filtration systems exist to help clean the tank, and wise investment in a filter will reduce the work that must be done to keep your fish healthy and happy and your tank looking as it should. However, there is no set up that is completely free of maintenance. If you have adequate filtration, and your tank is not overstocked or overfed, then the ideal maintenance schedule is a small water change (removal and replacement of around 20 – 25% of the water) once a fortnight. This task should take no more than about fifteen minutes, and if performed regularly, should eliminate the need for messy and time-consuming complete tank strip-downs (which are undesirable for the fish as well!). Cleaning of the gravel can be performed at the same time as a water change by using a gravel cleaner, and it takes only a few seconds to remove algae, so long as it is not allowed to grow too rampantly. You will also need to perform some maintenance on your filter system. The amount and frequency of this will vary depending on the style of filter chosen, but commonly it can be done at the same time as a water change and will take only a few minutes extra. If you decide to begin with an unfiltered aquarium, you should be prepared to change between 50 and 80% of the water once a week (or practically 100% in bowls or very small aquariums). Of course, you will also spend a few minutes a day feeding your fish, and hopefully many hours a day simply sitting back and watching them!

How much will it cost to set up and run?

The initial (and ongoing) costs will clearly depend on the size of aquarium, type of filtration, and on whether you choose coldwater or tropical fish. Coldwater aquariums are cheaper to set up initially, since you do not need to buy a heater, and a very small coldwater tank can be maintained without a filter (although this is not the most recommended system!). If you want a very basic small tank or bowl with no filter, you would generally spend between $25 and $60. This would include the essentials of fish keeping: the tank or bowl, some gravel, fish food, and chlorine neutraliser, and possibly a plant or small ornament. This type of set up does not have a high on-going financial cost, however, it does require much more maintenance, and will support only a limited number of coldwater fish. If you want an aquarium that is easier to maintain, it is best to allow $100 – $150. This will get you a slightly larger tank, a good power filter, and all the essentials. From around $100 to $120 you can get a system that could be converted a tropical tank with simply the addition of a heater. You can buy a tank with a more basic, air-driven filter more cheaply, but these filters do have their drawbacks. Power filters are recommended over air-driven models for a number of reasons, the main ones being that they provide better filtration, are silent running (while an air pump may be noisy), and have lower on-going costs. If you want a filter but cannot afford the initial cost of a power filter, then an air-driven filter is still much better than no filtration at all. Air-driven filters generally cost between $20 and $40. On their own, power filters cost from $35 for the smallest models. Filtration will be covered in more detail later, or for a complete discussion of filtration and the relative merits of different filter systems, see our filtration guide. A small tropical tank will usually cost from $150 to $200, which would include a small powerfilter and a heater. Most people would spend between $250 and $300 on a small to medium tropical tank, and invest in an even better filter and/or heater, a larger tank, and possibly a fluorescent light. Fluorescent lighting kits for aquariums are more expensive than fluorescent fitting for the home. This is due to two factors: Firstly, the light hoods are designed to be a safe as possible, since they must be placed above an aquarium and may be subject to splashes of water etc. Secondly, aquarium tubes contain special phosphors to produce the correct light spectrum for aquariums, which makes them more expensive than household fluoros. A light is not essential for keeping either tropical or coldwater fish. It is necessary if you want to grow live plants. However, a light is desirable, especially for tropicals, as their brilliant colours cannot truly be appreciated without one. Larger tanks require larger filters, heaters and lights, and so the price increases accordingly. You may also need a stand for your aquarium, especially for larger ones, and there are also cabinets available to turn your aquarium into a living furniture piece. A larger tank on a stand will generally cost between $400 and $800, including filtration and heating, while an aquarium cabinet will cost roughly the same as any other quality piece of furniture, bringing the total cost to between $700 and $1,200. Very large aquariums (especially those greater than 50 cm tall) need to be made either from very thick glass or acrylic, and will generally cost between $1,500 and $3,000 depending on the size, type of stand or cabinet, and filtration. The sky really is the limit – some people have spent in excess of $15,000 on aquariums! However, the opposite is also true, and a set up can be found for any budget. If you want a large aquarium and have a set budget in mind, then we recommend that you consider all aspects of the cost, especially filtration. Rather than simply buying the largest tank you can afford and having nothing left over for other equipment, consider getting a smaller tank, or a more basic stand, and spending the extra on the life-support system for your aquarium. After all, that is what keeps the fish alive and the tank clean, and ultimately allows you to enjoy your chosen hobby!

What size aquarium should I buy?

It is generally best to buy the largest aquarium you can afford (complete with the necessary filtration etc). A larger water volume means more stable water conditions for the fish, and the ability to house more, or larger fish. Of course, you must also consider the space you have available. Due to space or financial restrictions you may have to settle for a smaller aquarium. As mentioned above, if working to a budget, it is better to get a smaller tank than to skimp on the filtration and other equipment. If you only want to keep one or two small coldwater fish, and are happy to do the regular maintenance required, you would need only a small aquarium (12″ – 14″ or approx 10 l) or bowl. If you want to keep more fish, or do not want to do as much maintenance, consider getting at least a 14″ (10 l) aquarium or larger, since powerfilters can be added to these. (It is difficult to filter a smaller aquarium or bowl). For tropical fish, a tank of at least 25 l (eg 16″) is best, since the temperature of smaller tanks can fluctuate too rapidly. If you want to get a tank that can later be converted to marine, a tank of around 150 l (eg 36″) is recommended, although a mini-reef can be set up in a tank as small as 80 l (eg oversized 24″ or 30″), or in all-in-one units as small as 25l.

Will my fish grow to the size of my tank?

The simple answer to this question is no. The size of a tank, in itself, does not restrict the growth of a fish. On the other hand, a potentially large species will never reach full size in a small tank. As a fish grows, the amount of waste it produces increases exponentially. In a small tank, there will be a point where the water volume and filtration cannot cope with the increased load, the fish will become stressed, and most likely will succumb to disease. If the tank is kept scrupulously clean, a fish may grow to such a size that it can barely move in an aquarium, but this is rare. The growth of fish may be slowed in small or crowded tanks – there is some evidence to suggest that high levels of nitrate (common where there is a large bioload) levels retard growth – but the fish will still continue to grow slowly. It is best to choose fish that suit the size of your tank. One exception is goldfish kept in unheated aquaria. Although they grow large, goldfish do not grow quickly if they are kept in cooler water and not fed excessively. They are also very hardy and tolerant of waste products. Goldfish can, therefore, be kept in smaller aquaria, but they should not be crowded. If a goldfish does start to outgrow the tank it should be returned to the store to be found a new (larger) home, or given or sold to someone with a larger aquarium or pond. Remember that aquarium fish should never be released into the water ways.

Should I get coldwater or tropical fish?

There are pros and cons to both types of fish keeping, and the final decision rests with you. The advantages of coldwater fish are: low cost of initial set up, with minimal equipment required, nearly all species are hardy, and most are compatible. The main disadvantage of coldwater is the limited range of species that are available. Also, goldfish (which are by far the most common coldwater fish) are relatively messy, and will generally eat plants. It is a common misconception that tropical fish are more difficult to keep than coldwater. There are many species of tropical fish that are just as hardy as coldwater fish. However, it is also true that there are species which are very difficult to keep, or which are large and aggressive. However, if you stick to hardy, peaceful fish, they are, if anything, easier to maintain than coldwater species since they are much less messy. Also, most of these species do not eat plants. There is a huge variety of fish available for tropical tanks, although not all are compatible, nor are many types recommended for beginners. Even given these provisos, the choice of beginner fish is much larger in tropical than coldwater. The main disadvantage of tropical aquariums is the higher initial cost. Tropicals need at least a 25 l tank, you cannot keep tropicals without a filter, and a heater is also needed.

What does a filter do?

The obvious role of a filter is cleaning the tank, but there is more to the picture than that. The water in an aquarium can appear crystal clear, and yet still be unsuitable for the fish. It is important to realise that good water clarity, while highly desirable, does not necessarily mean good water quality. The second purpose of filtration, although less obvious, is even more important, and that is to remove toxic dissolved waste products from the water. What follows here is a basic description, we recommend that you have a look at our filtration information pages for a more in depth explanation of filtration and water quality. There you can also find descriptions of the many styles of filter available, and a guide to choosing the best filter for your tank. Fish excrete ammonia (NH3) which is toxic even at low concentrations. Fortunately, two sets of naturally occurring bacteria, which cover all the surfaces within an aquarium (including the walls, gravel & ornaments) quickly convert this ammonia into slightly less toxic nitrite (NO2) and then to relatively harmless nitrate (NO3). While these bacteria are always present, they can only process ammonia at a certain rate, their number is limited, and they rely on a flow of oxygenated water to carry out these conversions. A filter provides both a suitable flow of water and a site for the bacteria to colonise, allowing their numbers and efficiency to increase. Without a filter, the bacteria in an aquarium can convert only a limited amount of ammonia and nitrite, so the number (and size) of fish must be limited, and frequent water changes are necessary to remove any excess ammonia and nitrite before these reach toxic concentrations. Some filters are designed primarily to “sieve” the water through a sponge which captures fine particles (a process known as mechanical filtration), but in this case, the sponge also serves as a site for bacteria to convert ammonia and nitrite (biological filtration). Other filters may contain a material designed primarily for biological filtration, which will generally not remove as much fine particulate matter, but will do more towards improving water quality. Ideally, a filter should provide a good mix of mechanical and biological filtration. It is important to clean the filter media regularly to remove detritus, since if this builds up too much it will impede water flow, and may eventually choke the filtration bacteria. However, the cleaning should not be too thorough, or the filtration bacteria will be killed off. It is best to gently rinse any solid waste from the filter media using water from the aquarium (eg water that has been removed for a water change). Do not worry about discolouration of the filter media, since this is caused by the desirable bacteria. A third type of filtration exists, which is the removal of dissolved wastes using chemical methods, eg adsorption onto a reactive surface such as activated carbon or zeolite. This is known as chemical filtration. Carbon, zeolite, or other materials can be placed into a range of filters, and as well as their chemical action, they also provide a site for biological filtration. Although it can be beneficial, chemical filtration is not essential, and should not take the place of good biological filtration. Once chemical filtration media have been exhausted (ie have adsorbed as much waste product as they can) they must usually be discarded, and if not replaced, they can even leach toxins back into the aquarium. If these media are utilised, they should be replaced at least once a month, otherwise it is best not to use them at all. While filtration is important, it does not eliminate the need for water changes. Nitrate will build up and eventually cause problems. Even in relatively low concentrations, nitrate will promote the growth of algae, and in higher concentrations, it is toxic to many fish. Other waste products also build up, and although these are not toxic, they lead to a lowering of the pH of the water (ie make it more acidic). If the water is allowed to become too acidic, it will actually damage the fish, leading to disease or even death. For these reasons it is important to perform regular partial water changes, even when good filtration is in place.

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