Choosing a new fish is one of the most exciting parts of freshwater fishkeeping but it is also where many long-term aquarium problems begin. In this episode Art explores the single most important question to ask before buying a fish, along with six practical checks covering adult size, aquarium suitability, compatibility, feeding, quarantine and long-term care.
Whether you are stocking your first community aquarium or adding a new species to an established tank, this episode will help you make more responsible fish choices and avoid common mistakes such as overcrowding, aggression, poor diet and unsuitable water conditions.
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[00:00:00] Welcome to this episode of The Aquarist’s Edge, a podcast for home aquarists just like you. Learn more about how to keep a thriving aquarium and discover ideas and tips to give your aquarium the edge. And now, over to our host, Arthur Preston.
[00:00:18] Hi everybody, welcome to this episode of The Aquarists Edge. Today we're going to talk about one of the most exciting and sometimes most dangerous, perhaps moments in fish keeping, and that is choosing a new fish. Now, most of us know how this happens. We walk into the aquarium shop and our intention is to buy food, perhaps some water conditioner, maybe a replacement thermometer, and then we see it.
[00:00:42] It's a fish that we haven't seen before, something that looks quite unusual, maybe it has flashing colours, it just looks interesting. And before long, we're busy thinking about how we could put this fish into one of our tanks, how we could rearrange the entire aquascape around it. Very excitement is part of the hobby and there's nothing wrong with it. The problem begins when excitement becomes the only reason for buying a fish. You know, a fish might be perfect in the shop, but become completely unsuitable once it matures.
[00:01:11] It may need a larger group, different water parameters, more swimming space, or a type of food that the other fish aren't getting at the moment, and perhaps they become aggressive as they mature. And so today I want to give you seven questions that can guide almost every fish buying decision. Now, one of those questions is more important than all the others, and the remaining six are going to help you answer it honestly. So let's figure out what is that most important question.
[00:01:38] You know, it really isn't whether the fish is going to fit into your aquarium today. It's not whether the shop describes it as a hardy fish. It's not whether it can survive in your water, because survival really is a very low standard. The real issue is whether the fish can grow normally, behave naturally, receive appropriate food, and live without constant stress for as long as it remains in your care. Now, that concept of being consistent really matters here.
[00:02:06] You know, many aquariums look excellent immediately after a water change. The important conditions are the ones that remain stable during an ordinary week, after feeding, waste production, and daily life have continued. And honestly, a suitable home includes more than water volume. It includes temperature, water chemistry, filtration, oxygen, shelter, social conditions, and long-term care. It also includes your own circumstances. You know, these fish may remain with you for several years.
[00:02:33] And during that time, you may move home, have power failures, change jobs, or lose some of the enthusiasm you had when your aquarium was new. And so choosing a fish means choosing the responsibility that comes with it. A useful habit is to finish this sentence before buying anything new for your tank. I can provide this fish with an appropriate life because... Dot, dot, dot. And your answer should include the adult fish. Not only the juvenile one in the shop. It should include the aquarium, the group size, the food, and the long-term plan.
[00:03:03] When we say, I think it will be fine, that's not really a plan. The second question we need to ask is what will this fish become as an adult? Aquarium shops are full of baby fish. They are small, they're attractive, they're deceptively easy to imagine in almost any aquarium. But you're not buying the fish you see today. You're taking responsibility for the adult that it's going to become. An adult length is important, but it's not the whole story.
[00:03:29] A slim fish measuring 15cm doesn't create the same demands as a deep-bodied heavy fish of the same length. Body mass affects waste production. Activity affects swimming space requirements. And body shape affects the turning room needed in the tank. The size of the adult mouth affects which tank mates may eventually become fluted. And behaviour can also change dramatically with maturity. A young siktid may appear very calm in a shop aquarium. But as it develops, it may begin defending a cave or a breeding territory.
[00:03:59] A fish that tolerates others while young may become solitary as it matures. A small predator may become large enough to swallow fish that were previously safe companions. And this is why basic stocking formulas based only on a centimetre of fish are unreliable. And fish aren't identical objects. Their biology and their behaviour matter far more than a simple calculation of length. And before buying, book for photographs or videos of mature specimens. Pay attention to body depth, fins, swimming style and territorial behaviour.
[00:04:29] And choose for the adult, not for the temporary juvenile that you see in the shop. And something you'll hear mentioned all the time by experienced aquarists. Do your research. The third question is does my aquarium suit the fish rather than merely contain it? An aquarium can physically contain a fish without functioning as a suitable habitat. And that difference is important. A suitable aquarium must provide the right kind of space.
[00:04:57] An active swimmer may need a long tank with open water. But a bottom dwelling species may need floor area, smooth substrates and places to hide. A cave dwelling fish may need several shelters so that one dominant individual cannot control every safe space. Water quality is equally important. The aquarium should have an established biological filter capable of processing the waste produced by the existing fish and the new arrival. Ammonia and nitrite should remain at zero under normal conditions.
[00:05:24] And nitrate should be monitored and controlled through sensible stocking, feeding and water changes. The water should also suit the species. A stable pH within an appropriate range is usually better than repeatedly changing the water with chemicals in pursuit of a supposedly perfect number. Temperature, flow and oxygen matter as well. A fish from fast moving oxygen rich water may struggle in a warm still aquarium. An acquired species has spent its entire life fighting against a filter current that is too strong.
[00:05:54] You need to look at the aquarium from the fish's perspective. You need to notice the open space. Where is their shelter? Examine the current. Check the light. And look at the feeding areas. The goal isn't simply to find somewhere to place the fish. The goal is to provide an environment in which its behavior makes sense. Question four is this. How does this fish need to live with others? The word peaceful causes a lot of confusion in fish keeping.
[00:06:22] A fish may be peaceful towards other species but aggressive towards its own kind. It may be calm in a proper group but nervous or disruptive when kept alone. It may coexist well until breeding begins. It may ignore adult tank mates while eating smaller fish. Compatibility is not a simple personality label. It depends on social structure, aquarium size, territory, group size and the behavior of the other inhabitants. Many small freshwater fish are social and shouldn't be purchased as a single display animal.
[00:06:52] Tetras, resboros, danios and many catfish often behave more confidently in suitable groups. A larger group can spread social pressure and encourage more natural movement. Other species may need to live alone in pairs or in carefully managed ratios. Two fish may also be incompatible without obvious fighting. And a fast, enthusiastic feeder can prevent a slow fish from eating. A boisterous species can keep a timid fish hidden all day.
[00:07:18] Successful compatibility means more than the absence of injury or harassment. Every fish should have access to food, shelter and usable space without a living in constant fear. It's always good to have a backup plan in case this introduction of a new fish fails. That may mean a divider, another aquarium or responsible rehoming. You need to think about this before you introduce the fish and need to find a quick solution.
[00:07:45] Question of five is can I provide the right food in the right way? Feeding is not only about selecting a product with a fish picture on the container. Different species are going to want to feed in different ways or need to feed in different ways. Some take food from the surface. Others feed in the midwater zone. Some graze throughout the day. Others search the bottom after the light guard. A food may be nutritionally suitable but still fail if the fish can't reach it. Food enters the tank.
[00:08:14] Active fish consume everything and a few crumbs reach the substrate. And that one shy bottom dweller starts to be malnourished. But the aquarium has been fed. But the bottom dweller has not. Think about the food's size, its texture, its sinking rates. Consider whether the new fish can compete with the existing inhabitants. Some fish may need targeted feeding or food added after the lights are down. Also be aware of that phrase, algae eater. It's particularly misleading.
[00:08:43] An algae-eating fish is not an alternative to cleaning the aquarium. Many grazing species need prepared foods, vegetable matter, biofilm or other specialised nutrition. The algae growing naturally in your aquarium may not be sufficient or even suitable. Overfeeding creates a different problem. Uneaten food becomes waste and even eaten food eventually contributes to the biological load. Watch your fish rather than relying only on a fixed portion. Notice who eats, who misses out and where the leftovers settle. Question 6.
[00:09:13] Is this individual healthy and can I quarantine it properly? A suitable species can still be a poor purchase if the individual fish is unhealthy. So spend time observing the entire aquarium in the shop. Look for normal balance and controlled swimming. Watch the breathing. Notice clamped fins, cloudy eyes, visible spots, sores, damaged mouths or unusually thin bodies. Don't just inspect the fish you want to buy. All the fish in that system may share water and disease exposure.
[00:09:41] A newly arrived fish may still be affected by transport stress and some diseases do not show visible symptoms immediately. Even a healthy looking fish should be quarantined before entering an established aquarium. A quarantine tank gives you time to observe feeding, breathing, waste production and behaviour without placing the existing fish at risk. Question 7. Am I prepared for the responsibility when life changes? Question 7. We all make plans when everything's working fine.
[00:10:07] We have our filter running, the heater's stable, the budget's available, you're motivated as a fish keeper. But truthfully, life doesn't always remain that convenient. Equipment can fail, electricity goes off, people travel, homes change, jobs change. A responsible plan includes a few basic backups such as a spare air pump and a spare heater. Dedicated buckets, water conditioner and reliable test kits should be readily available before an emergency.
[00:10:32] Now, somebody who cares for your aquarium while you are away should receive simple instructions and pre-measured food. Overfeeding by a helpful friend can be far more dangerous than a short period of lighter feeding. You should also consider what happens if you move or can no longer keep your fish. Large or specialised species can be difficult to rehome. And remember not to release your aquarium fish into a natural river or waterway. That's never going to be acceptable.
[00:10:58] Responsible rehoming means filing an aquarium that can genuinely meet the animal's needs. And long-term care also means choosing a system that suits your real lifestyle, not the one you wish to have. A complicated aquarium may be exciting for the first few months, but the best maintenance routine is the one you can continue when life becomes busy. Simple, stable care is better than impressive care that can't be sustained. So yes, choosing a fish should be exciting.
[00:11:26] That should always be one of the fun parts of this hobby. And the purpose of the questions asked in this episode is not to remove the joy from this hobby. These questions are to make sure that the excitement that you have is followed by a decision you can feel good about months and years later. The most important question is whether you can provide that fish with an appropriate life for its entire lifespan. And the other six questions help you find the answer. Consider the adult animal. Match the aquarium to the fish. Respect its social behavior.
[00:11:56] Plan how it will eat. Choose a healthy individual and quarantine it. Prepare for the future. And the answer to these questions will be sometimes yes and sometimes not yet. And sometimes the best decision will be to admire the fish without even owning it. Now, that's not a missed opportunity. I would say that it can rather be classified as being a responsible fish keeper. Folks, thank you for spending time listening to this episode of The Aquarist’s Edge. Go ahead and share this episode with somebody who's planning the next aquarium addition.
[00:12:26] Perhaps a fellow fish keeper or someone who's interested in getting into the hobby. And I would encourage you to like this video and subscribe to the YouTube channel if you have not done so yet. And if you're listening on a podcast app, please go ahead and review the podcast. Please possibly leave a comment and let's make sure that this podcast series gets in front of many other keen or new acerists.
[00:12:47] It really is my goal to provide a place where we can learn together, where we can share some solid advice, where we can just enjoy being keen fish keepers. As always, I'm very grateful to those of you who subscribe to the YouTube channel and follow the podcast on the various podcast apps. If you continue to find these episodes helpful, please would you consider buying me a coffee? The link will be available in the show notes and on the screen on the YouTube video.
[00:13:12] Folks, until we meet again next time for another episode in the Acra's Edge, keep learning, keep discovering, and keep enjoying this amazing hobby. Bye for now. That's it for this episode of the The Aquarist’s Edge. Please consider subscribing to this podcast so that you don't miss further episodes. We would love it if you would also rate and review the podcast as this helps make it visible to others.
[00:13:35] Until next time, keep learning and discovering, and keep finding your Acra's Edge in this captivating and fascinating hobby.