Tropical Fish How To Guide

by Owen James

Anyone can have a community tank of tropical fishes and plants

Anyone can have a community tank of tropical fishes and plants

(Image by EikeR)

Getting started with tropical fish is easy, provided you do a little research on how to keep tropical fish in advance. Our 10-step how to guide introduces the key decisions.

You could also ask for help at a decent aquarium store, but you’ll get a much better understand if you understand the basics first.

Think through what you want to achieve and then proceed patiently, rather than just rushing to the local fish store this afternoon and leaving with a bruised credit card and a car full of fish kit.

Note: You will ideally do some more research before getting your first fish, either by following the links to come as we fill out this section (subscribe to keep in touch), or by reading one of the many good books available.

1. Decide what sort of tropical fish you want to keep

Cardinal tetras are good community fish

Cardinal tetras are good community fish

Not all tropical fish can be kept together. Some are aggressive, others have special water requirements, but there’s hundreds of species that do happily get along.

Community fish: Most of the smaller fish like tetras, guppies and corydoras catfish that you typically see bustling about in one aquarium are called community fish. A tank of them with plants looks beautiful, is affordable, and gives you plenty of choice in the store, making community fish the best way for a new aquarium keeper to start. (The cardinal tetras above are from Leino88).

Specialised fish: About 10% of the freshwater fish you see in a tropical fish store require specific care requirements. Discus, African Rift Valley cichlids, killifish, certain catfish, and oddballs like Elephant Nose fish need tanks with particular water conditions or environments. Others, like pirahnas and many Central American cichlids, are flat out incompatible because they’re too aggressive.

Tankbusters: Some fish are tough and friendly enough to anything they can’t swallow, but they grow far too big for the average aquarium. Pacus, Giant Gouramis, and many big catfish fit into this category. These fish are less readily sold than in the old days, which is good news, as too often they outgrew aquariums and were dumped in the natural environment (a big no-no). Best left to specialists.

Marine fish and invertebrates: Require more dedicated and knowledgeable care. This how to is only for freshwater fish, which originally came from the rivers and lakes around the world. (Marine fish come from the sea and so require special salt, as do certain brackish water fish like Scats and Archer fish).

Plants: Tough plants like Amazon Swords will grow in almost any aquarium if given some light and gravel to root in. But if you want to have a really lushly planted aquarium, you’ll need to plan from day one to give your plants the light, substrate and water conditions they require to thrive.

2. Decide how big an aquarium you’ve room for

Next you need to decide how big a fish tank to get, depending firstly on the room you have in your house. Water is heavy, so anything other other than a tiny aquarium requires its own special stand, either bought or home made. With really big aquariums, you may even need to check the floorboards.

You’ll also need to make sure it’s not too near your central heating or a window, both of which can overheat the tank, and it’s a good idea to avoid draughty spots, too. Electrical sockets nearby are a must for tropical tanks.

The size of the aquarium determines how many fish you can ultimately keep. Fish require oxygen and clean water, and so any volume of water can only support so many fish before they start to suffer.

A typical 24″ inch by 12″ fish tank will happily hold about a dozen 2″-sized tropical fish.

3. Choose your filter system

An external filter pumps the water outside of the aquarium

An external filter sits outside of the aquarium

There are lots of different filter systems available, but for freshwater tanks you have four main options:

Undergravel filter: This sits beneath the tank gravel, filtering the water biologically by building up a population of bacteria in the substrate, and also straining out particulate debris. Water is moved through the gravel via a filter plate attached to airlifts, powered either by air pumps or powerheads. An easy way to start, but not great for plants and can be messy to keep clean.

Internal filter: Small internal filters can cost as little as the price of half-a-dozen community fish. Internal filters typically have a sponge inside, which filters the water and builds up a population of bacteria that keeps it sweet. Very cheap models are driven by an air pump; they’re effective, though the bubbles and pump can be noisy. Internal filters a very affordable option for small aquariums. But against that they take up tank room, and can be ugly.

External filter: These sit outside the tank, usually in the cabinet below but sometimes hanging off the back. They come in all shapes and sizes, and range in price from a little more costly than an internal filter to the price of a portable TV! The best enable you to use several different types of filter media inside them, and they move a lot of water, making them great for bigger tanks. One snag can be leaks outside of your aquarium if a pipe comes loose. They can be expensive, but a big advantage of external filters are they’re easier to maintain without disturbing your tank furnishings.

No filter: It’s possible to use no filter, keeping the tank water clean with plants, the natural way. It does work, but there’s little room for error, especially if you fill the tank to maximum capacity. Water looks nicer when it’s moving, too, which means at least getting an air pump. A filter-less tank is not recommended for beginners.

4. Buy all the equipment – but no fish yet!

Once you’ve decided on your tank and an appropriate filter, you can start buying all the equipment you’ll need. The essentials are:

  • The tank and stand
  • A lighting system that either sits inside the aquarium hood or is mounted above it
  • A good quality heater-thermostat, for keeping the water at tropical temperatures
  • A thermometer that sticks on the glass
  • A net for catching fish
  • An air pump (optional, unless used to drive an undergravel filter)
  • Gravel (a good layer is vital if using an undergravel filter) or special aquatic soil for growing plants
  • Furnishings to make a natural home, such as decorative bogwood and suitable rocks. (Plastic castles and treasure chests are strictly down to personal taste, but do make sure anything is made specifically safe for long-term aquarium use)
  • Water treatments for neutralising chlorine in tapwater
  • Basic test kits for Ammonia, Nitrite, Nitrate and pH
  • A few fish disease medicines (get them before you need them!)
  • A small separate aquarium for quarantining new fish is a great bonus

5. Set-up your aquarium in its permanent position

This empty tank has filter, substrate and wood nicely positioned.

This empty tank has filter, substrate and wood nicely positioned.

Get the tank in position and set up according to the manufacturer’s instructions (it will probably need a layer of polystyrene under the bottom glass, to prevent cracks). Don’t try and move even a small aquarium once it’s got any water inside – fishtanks are very heavy, and even if you can pick it up the glass will likely break.

It’s a good idea to fill the tank straight away to check for leaks. Put the tank in its final position, then direct a hosepipe into it until it’s filled. Check all the corners and sides of the aquarium for leaks. You’d be very unlucky to have a new tank leak, but secondhand tanks sometimes develop leaks from being moved. If your tank does leak, you’ll have to drain and thoroughly clean it, then rework the seal using silicon gel. If the tank is new, get the store to fix it.

No leaks? Great. Syphon out all the water, then put the equipment in place. Filter pipes are best tucked into the corners. Heaters are best attached to the glass at a 45-degree angle, so rising heat is whisked away from the thermostat by the aquarium water.

Next add your furnishings and gravel or aquatic soil. Spend some time experimenting to get a look that works. Some people even like to arrange the stones and wood outside of the aquarium first, or sketch it out on paper.

It’s a good idea to hide equipment as much as possible with your tank decorations, but make sure you can see the thermometer and heater light, and that your filter can operate properly and is easily accessible.

6. Fill the tank with water, and switch everything on

No fish yet, but plants alone give this tank some beauty and interest

No fish yet, but plants alone give this tank some beauty and interest

What’s an aquarium without water? If you’re keeping delicate tropical fish like discus you’ll want to purify the water first, but for general community fish, it’s generally okay to set-up the tank with tap water, since you won’t be adding any fish for a while and the filters will soon drive out chlorine from the water.

To fill the tank, place a bowl on the tank substrate, then direct water into it, either via a slowly trickling  hosepipe or else by pouring buckets of water in. The bowl takes the force of the water, preventing the gravel or aquatic soil from being blown about.

Advanced aquascapers add their plants to the tank before adding any water, but for new fishkeepers it’s easier to fill the tank first and add your first tough plants after the water has reached the correct temperature.

Now switch everything on, and make sure all the pumps are working properly. The water temperature should rise to about 25-degrees C (77-degrees F) after a day or so. If it’s too hot or cold, adjust the thermostat.

7. Wait! Mature your tank before adding fish

Your new tank will look lovely and clean, but the filters won’t yet have built up the populations of bacteria required to break down fish waste. For this reason you need to add fish over a period of weeks, allowing the ‘nitrogen cycle‘ to start operating effectively in your tank.

Maturing the tank with fish: The traditional way to do this is to add a few tough fish like Zebra danios to the tank first. Their waste products will eventually be broken down by the filter bacteria, but it will take a while for it to start happening, which means they will be exposed to pollutants. For this reason, only start with 3-4 fish, and feed them lightly. If you test the water every day for Ammonia, Nitrite and Nitrate, you can track the nitrogen cycle developing over time. Eventually Ammonia will be undetectable in your tank, which is when it’s said to be mature.

Maturing the tank with chemicals: A way to avoid putting any fish through discomfort with a new aquarium is to buy a special product for maturing the tank using chemicals. These products deliberately add nitrogen to an aquarium to get the tank going. You can achieve a similar thing by adding a marble-sized bit of cooked meat. Theoretically the results will be the same, although tanks matured with fish seem more stable in the early weeks. Some products also add bacteria to the water, but don’t worry, bacteria will already be present in the tank, so it’ll only take a few days longer if you wait. Again, test the water – you should see Ammonia rise and then fall away and stay at zero. When Nitrite is also zero, it’s safe to add some fish.

Maturing a natural aquarium: The waste products that are so dangerous to fish are actually food for plants. For this reason, a really well-planted tank can support a few fish just a day or two after the plants are established. However, it still makes sense to go slow, for the sake of your fish’s health. Also, even in natural aquariums, bacteria attached to plant leaves and on the surfaces of the aquarium play a key role in breaking down waste, and these take time to establish.

With all three methods, you can add as many live plants as you like right away, so be patient when it comes to fish and indulge your spending desires on vegetation. Ideally add a lot of plants at the start, to help keep algae under control later (floating plants are particularly good for this).

8. Slowly build up to your tank’s stocking capacity

A pair of angelfish make a splendid centrepiece for larger community tanks

A pair of angelfish make a splendid focus for larger community tanks

(Image by Redvers)

So, the nitrogen cycle is established in your tank, and your first fish and plants are happy. Don’t rush things, though – patience is a virtue in fishkeeping.

Your tank is always in a delicate balance between the inhabitants and the plants and bacteria that deal with their waste. Add more fish, and you disrupt the balance. Bacteria will quickly multiply to utilize the extra waste the new fish bring, but it does take a few days. Therefore it’s best to build up to your maximum stocking capacity slowly, over a period of several weeks.

Ideally new fish will be quarantined and treated for disease in a small hospital tank so they don’t infect your established fishes. All the books tell you to do this and it is an excellent practice, which will greatly reduce problems with your fish, but in reality most one tank aquarists don’t bother.

Be vigilant when buying fish for any signs of disease (such as flicking, gasping, or any visible spots or irritations) and if in doubt, don’t buy.

As you move towards your tank’s maximum stocking level, try to see the aquarium from the fish’s perspective, to avoid overcrowding any niches in the tank. Don’t only buy surface dwelling fish, or fill your tank with catfish, say. Try and get a nice range of compatible community fish that occupy different layers of the aquarium.

Creating a natural biotype is a good way of planning your stock. With this method you buy community fish from the same part of the world, and decorate the tank appropriately for that region.

For instance, a two-foot, 15-gallon South American biotype might be decorated with bogwood, river sand and Amazon Sword plants, and contain the following fish:

  • 4 surface-dwelling marbled hatchet fish
  • 8 neon tetras
  • 2 Apistogramma dwarf cichlids
  • 3 bronze corydoras catfish

9. Perform your daily, weekly, and monthly tank tasks

Get your hands wet to keep your tank clean

Get your hands wet to keep your tank clean

(Image by nttrbx)

The secret to having a beautiful tropical fish tank in the long-term is to regularly perform the required maintenance tasks, rather then letting things slide and then trying to catch up.

A good routine for a standard tropical fish tank would be:


  • Feed the fish (twice a day)
  • Add plant fertilizer (optional)
  • Check the tank temperature
  • Check for any signs of ill-health


  • Top up the water level
  • Trim plants (if required)
  • Clean tank glass of algae
  • Test tank water parameters (especially when the tank is still young)


  • Change 25% of the tank water with treated tap water
  • Replace disposable filter media, such as filter floss and activated carbon
  • Clean biological filter media in a bucket of used tank water (which is then discarded)


  • Replace fluorescent light fittings
  • Consider replacing your heater and thermometer

10. Enjoy your aquarium!

These platies are enjoying a wonderful tropical fish tank

These platies are enjoying a wonderful tropical fish tank

(Image by nttrbx)

After all this hard work, make sure you enjoy your aquarium. It’s easy to get distracted by life, and for the tank to become a chore, rather than a joy.

You can always try a new challenge, such as improving the plant vegetation or making a better aquascape using bogwood and other materials. Failing that, strip the tank down and start again, or set-up a new aquarium. (Warning: Dedicated fish fanatics always hanker for a new aquarium).

This is a general How To guide, so please use it as a first port of call, and read at least one good book before setting up your tropical fish tank.

Check out Katy's Tropical Fish Guide for more aquarium info.

Get our latest articles direct by email. Type in your address and submit:

{ 10 comments… read them below or add one }

Snouty98 11.16.08 at 2:28 pm

Hey, you missed out step 11 – watch the tank turn into a green slimy mess! 🙂

Just kidding, neat guide.

SarahB 11.16.08 at 2:30 pm

Life is definitely easier if you take it slowly with aquarium fishes. I’ve got a 20 gallon long with danios, guppies, mollies and a couple of albino catfish. Life got easier once the tank was up and running. The first weeks are the hardest. Now the tank never gives me any bother. I make sure I do all my water chores though.

Mike 11.18.08 at 6:31 pm

Fantastic article! So many people think you just fill a tank with water a plunk any old fish in there when the truth is quite different. I agree with Sarah take it slow, follow the proper set up tasks like you have described above and your overall aquarium experience will be that much better.

Eric 01.24.09 at 12:06 am

Great Site. I bookmarked this! Thanks so much!

Megan 02.28.09 at 7:02 pm

i have only just bought a new fish tank and found this guide very usfull because it told me exactly what i ead to do!!! thanks

James 09.16.09 at 9:26 pm

Good article. I have just bought a new 240Litre Tank after upgrading from my 180L one and am very happy. Its great and very relaxing after a hard day at work to come home and just stare at the fish in the tank. My newest member a Red Parrot Fish seems very happy and gets on with all tank mates, including the Male Betta (have had for 8 months) and my Grumpy (but good) Angel :):)

ABHISHEK 02.05.11 at 9:36 am


Ryan Simmons 11.18.11 at 10:33 pm

I would have to disagree with the 25% water change every month. That is really too little too infrequently. Especially as a guide for people new to aquaria.

The reason why is that the vast majority of new aquarium keepers add way too many fish and underfilter their tank. If you only change 25% ever month the water parameters of the tank will change drastically from the tap water. You want to keep the parameters as closely together as possible.

When I’m keeping up with my normal maintenance I regularly do 80% water change weekly. There is really no reason to not change out as much water as possible unless it has been a long time since the water has been changed.

The benefit of this is obvious. If anything goes wrong with your tank like adding too much of a medicine, or the kid dumping the entire can of fish food into the tank, or the tank breaks, the fish are going to need brand new water immediately. If the tank’s water parameters are way off from the tap water (say as in Old Tank Syndrome), the sudden change in the quality of water will produce osmotic shock in the fish and likely kill them.

Over filter your tank and change as much of the water as often as you can make yourself do it.

R.C. 12.13.11 at 5:06 am

I have a 30 gallon tall tank with just a few hardy fish (guppy, danio, loach) and some basic plants and no filter for about two years. Love it. No algae, no fuss….but I definitely do not feed them every day. I don’t have the light on much either but all has been going great. No fish have died ( 2 years) and they seem happy.

Mark 12.20.12 at 11:23 am

I’m a total beginner but the local fish club have advised me to just feed just once every couple of days – just as much as the fish can eat in a few minutes. The fish they have seem to be thriving on that sort of interval -of course, I’m sure some fish may have different requirements.

Leave a Comment

You can use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>

Previous post:

Next post: