How to set up an aquarium for tropical fish - Swell UK

Starting from scratch with tropical fish? Here's our guide to everything you need to get started.

Fish Tank

The fish tank itself is of course, essential, but they come in many shapes and sizes, and cater for all tastes.

As tempting as it is to go for a whacky shape, a standard rectangle is best for the following reasons:

It has a large surface area in relation to its volume. That's important for allowing oxygen to diffuse into the water and CO2 to diffuse out, at night.

A large surface area means that you can stock more freshwater fish in a given volume than one with a small surface area, again, because of surface area, and oxygen levels. 

Then you have many types of fish that require room to swim and exercise, and those that need substrate surface area in which to feed and breed, like cichlids, and catfish. 

And buying the largest fish tank you can afford isn't a cliche or a sales tactic.

Larger water volumes are more stable than small ones in terms of temperature and water quality, they will enable you to keep a much larger variety of fish species, and in high number.

As many small tropical fish are shoaling species, to create a community tank, you'll need one that is large enough to keep groups of fish. Like six or more tetras, three or more Corydoras catfish, six or more rasboras, five or more guppies, and the best algae eaters like Bristlenose catfish are medium sized, and require medium and large tanks.

As a general guide, aquariums of 54 litres or more, and 60cm in length or more, are regarded as the most suitable for beginners, and capable of holding a community of 15-20 small tropical fish or fewer small species of cold water fish.

But choose an aquarium of 180 litres or more, and 90cm in length or more, and fish selection greatly increases to include popular species like Angelfish, rainbow fish and a community of 30 or more small to medium sized fish which will be varied in shape, colour and activity, and will occupy all levels of their new home. 

Fish tank cabinet

All aquariums must be placed on aquarium specific cabinets, and manufacturer's warranties may be void if a heavy aquarium full of water is supported by unsuitable home furniture.

In the worst case the furniture underneath may collapse. Instead choose the proper cabinet for your make and model of tank, which has been designed specifically to support its weight.

Cabinets benefit aquariums in other ways too, as they offer a place out of sight to place external power filters - the best filter option for a tropical or coldwater freshwater tank, and also to place pots of food, test kits, and all those plugs and cables.  

Aquarium heater

If you live in the UK, a heater is an essential piece of kit in order to keep tropical fish. Tropical fish come from tropical areas of the world like South America, South East Asia and Africa, which are hot year round, and water temperatures typically don't dip below 24 Celsius.

A heater has a thermostat combined, which can be set to 24 Celsius and will heat and regulate that preset temperature day and night, year round, keeping your fish at tropical temperatures they are more accustomed to.

Some advanced heaters display the temperature of the tank water, and if it is too hot or cold, but every aquarium owner should also arm themselves with a thermometer, to offer at a glance, temperature checking.

If you're unsure which size heater you need, select a model which has the same or more power in watts as there are litres of water in your aquarium.

So a 100 watt heater is needed for a 100 litre tank. A 200 watt heater for a 200 litre tank, and so on. If you have a 180 litre tank for example, you would select the next heater model up, which is 200 watts, as heaters only come in a few sizes, and typically only up to 300 watts.

If you have a large, 500 litre aquarium, you will need two heaters - a 200 watt, and a 300 watt.

Aquarium Filter

A filter is considered essential hardware for all aquariums, as they are life support systems for fish. No aquarium should be set up without a filtration system, and they need to operate 24 hours per day, from day one. 

Just like with aquariums, filters come in many shapes and sizes to suit those aquariums, and can range in price and performance.

If you are just starting out, internal filters are popular as they are simple to use and install, and offer good results. If you are starting out, but with a large aquarium and you want the best for your fish, an external power filter is the one to go for.

To select which filter you need for your tank, models are recommended for fixed tank lengths or water volumes, so choose a number "2" for a two foot long tank, or choose a filter for a 200 litre tank if yours is between 100 and 200 litres in volume.

Like with heaters, choose the next size up if your tank is an inbetween size, like 180 litres for example. And if you choose to keep messy fish like cichlids or goldfish, you may actually need twice the recommended filtration, which could mean two units. 

Aquarium lighting

Imagine a tropical fish tank full of movement and colour, and it's the lighting which will help to bring it all to life.

Many aquariums come with lighting built in, but bulbs can often be swapped for others which will enhance plant growth, or fish colour, or upgraded entirely for brighter lighting.

Open topped tanks will need separate lighting and tank mounts, and some lighting can also be controlled either by a separate inline controller, or an app on a smartphone or tablet.

Plants need a fixed 8-10 hour period of light per day, but fish can have their light turned off when you aren't viewing the tank. If lighting isn't controllable use a simple plug-in light timer, as excessive aquarium lighting, on for 12 hours per day or more, will cause nuisance algae.  

Use saltwater specific lighting for marine aquariums. 

Aquarium air pumps

Air pumps are an optional extra when setting up a tropical aquarium, but they do have a major benefit. By way of airline and an airstone, airpumps blow air into the water, where bubbles diffuse oxygen, essential for fish.

Filters that agitate the water surface also create oxygen, but air pumps do it in a more dedicated way, and are especially useful for overstocked tanks and those containing large fish.

If you run an airpump and a separate filter, if the filter stops working, the fish will still have access to oxygen, saving their lives in the short term, until you notice and remedy the filter problem.

Aeration is advised when using medications, when there is ammonia and nitrite present in the water, and beneficial filter bacteria are aerobic, meaning they use and consume oxygen.

Air bubbles rising up through aquarium water can be relaxing to watch, and some ornaments can be air operated, animating them and providing fun viewing for children. The fish don't mind it either!

One essential bit of kit with all airpumps is a non-return valve.

When placed in a cabinet below the aquarium, if there is a power cut, airpumps can suck aquarium water instead of blowing air, so a non-return valve prevents that from happening, stopping puddles and damage to the airpump too.

Fish tank decoration

Decoration makes fish feel at home in their bare glass boxes, and allows the owner some artistic interpretation at the same time. The first thing to go down in any new tank, after the aquarium, is gravel.

Aim for a layer 5cm deep at the front, and 7.5cm deep at the back, enabling anchoring or plastic plants, or rooting depth for live plants. Gravel can come in natural or bright, artificial colours, and can vary in grade from coarse to fine sand. Gravel should be washed thoroughly by hand in a clean bucket, before adding it to the tank. 

Popular decoration includes rocks, ornaments and bogwood, but ensure that any wood you use is suitable for aquarium use, as some floats, and can release chemicals into the tank water which are dangerous to fish.

Bogwood does release brown tannins into tank water for the first few months after being added. A natural process, many tropical fish like Cardinal tetras live naturally in tea stained "blackwater" in the Amazon, and will actually benefit from tannin stained water.

But if you don't like it, and crave crystal clear water, place activated carbon in the filter and replace regularly. Rocks, wood and ornaments are the next to be added after the gravel.       

How to fill up a fish tank

Tropical tanks can initially be filled from new with water from the tap, but there are a few things you need to do to that water to make it safe for tropical fish.

The first essential item is a dechlorinator. A simple liquid, dechlorinators make tapwater safe for fish and filter bacteria by neutralising chlorine.

Some water authorities also now use chloramine instead of chlorine, so if you are unsure, opt for a dechlorinator that neutralises both, and make sure that its used whenever you fill the tank with tapwater, or add tapwater during a water change.

Use as directed once the tank is first filled with water, plug the heater and filter in, and wait.

After dechlorinating, you can also add beneficial bacteria. This is recommended to kickstart new biological filters, helping to make them ready to convert harmful fish waste into less toxic substances. 

Your tank should heat up to the right temperature within 24 hours. Dechlorinators work instantly, but a new tank should be stocked very sparingly with a few hardy fish in the first few days and weeks, to avoid New Tank Syndrome.  

Aquarium test kits 

If you own an aquarium and keep fish, you need test kits. Aquarium water can be crystal clear but deadly, and the only way you will know if its safe to keep fish or not, is with test kits. 

A new aquarium will need four test kits - pH, Ammonia, Nitrite, and Nitrate. They will enable you to monitor water quality in new and mature tanks, and provide an early warning system if water quality starts to go downhill.

Test daily while the tank is maturing - to watch the levels of toxic ammonia and nitrite spike, and then start to fall, and then once the tank is mature, a weekly test is recommended.

Other aquarium essentials

Every aquarium owner needs a fish catching net, as you never know when you'll need it. The net diameter should be wider than your largest fish, and tricky to catch fish, like fast swimming danios are best caught with two nets, one in front of them, and one behind. 

You'll also need an algae pad or algae magnet to regularly wipe green algae growth from the front glass, and a siphon tube to remove water, for water changes.

The most useful syphon tube is one with a gravel vacuum combined. These simple but very effective tubes enable dirt to be sucked out of the gravel at the same time as you remove the water.

Arm yourself with a variety of dry foods and frozen foods to cater for fish which swim at different levels and have differing dietary needs.