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Setting up your first Tropical Fish Tank



So, you’ve decided to buy an aquarium and have a nice tank of interesting Tropical Fish?

Sadly the process of getting it home, filling it with water and stocking it immediately with fish just cannot be done.

We’ll try to explain to you why, but very basically water which comes from our taps is unsuitable for Fish without further treatment.


The first thing to consider is that water companies treat water with Chlorine which is toxic to fish, so you have to neutralise that, this is easily done by adding a prescribed amount of any of the commercially-available Water Treatments usually called Water Conditioner, especially made to do this job.


Next thing to bear in mind, and a really important one, is that you should not use water from your hot water tank as the tank is made from copper, and copper – along with other ‘heavy metals’ can be lethal to aquatic life.

You may say that your drinking (cold water) tap is supplied with water which passes through copper pipes but much less is leached into the water from the shorter length of copper, what little gets in is dealt with by the previously-mentioned Water Treatment another thing is the cold water will collect less contaminants than the water which is heated in the hot water tank.


You will need to decide where to set your aquarium - preferably away from draughts and also in an area which does not receive too much direct sunlight.

Next you need to choose a substrate for the base of the tank, it can be gravel or sand, and top it up with treated water – now for the fish? The answer is still most definitely “NO”.

Go back two steps – your substrate has to be thoroughly washed - and washed again. For gravel use a fine-meshed colander set over a bucket and quarter-fill the colander with your gravel.

Over this run water through a hosepipe at high enough pressure to make the gravel ‘tumble’ but not so much that it ‘tumbles’ out of the colander.

The water running through and into the bucket is constantly thrown away and this activity should continue until the water runs clear.Put this in the tank and then wash the next lot - until you've washed the whole amount. This is one of the more tedious tasks in setting up your tank, but the work put in now will be worth it in the long run - honestly.

This method can be equally well used to wash sand too, but without the colander as the sand would be washed through its holes.

Do this outdoors, gravel and sand have a nasty habit of getting washed over the sides of the bucket and if enough reaches the U-bend under the sink it will block it.


So now, you have your substrate washed and put in place…what next? It’s time to position the heater and filter,

as well hidden as is possible and place the thermometer in a spot where you can monitor it.

Now is the time to put in any rocks or wood (previously washed), do this carefully and achieve the sort of image you  are planning to create, it’s much easier to do this before you put the water in than when the tank is filled up.


Finally it is time to top up with water.

The best way to do this with as little disturbance to your very careful landscaping is to put a saucer on the gravel and put a tall mug onto that, sitting centrally.

Treated water is then poured into the mug gently and this then trickles into the saucer, tumbles over the sides and onto the substrate causing little or no disturbance.


When your tank is about half-full it’s time for the plants (if you’re going to use them).

The choice of available plants is huge and you would be well advised to start with some of the easier-grown species, your local Fish shop will be able to advise you more fully than this small guide can, so ask away, they are there to help you. Once you’re happy with the set-up, resume filling with water. Once it’s filled - time to switch on the heater, filter and light.

Have a drink and sit back to enjoy your handiwork.


Now comes the waiting time… although there are several products available which can reduce, or even cut out, the need to make water suitable for Fish to survive (commonly known as ‘cycling’ – more of which in a moment), you can take the natural route if you prefer and if you have the patience - a very important attribute for fish keepers.


‘Cycling’ the tank, this is quite technically based but in ordinary terms it can be summed up like this: water in a fish tank goes through several changes before it is fully suited to aquatic life.

At first it is fine but almost immediately due to aquatic activity Ammonia starts to build up within the water, Ammonia is lethal to all Fish life so this must be got rid of.

Within your filter two types of bacteria will grow and live, very basically one lot will get to work on the Ammonia and convert it to Nitrite, which in itself is equally poisonous to fish, but then the second lot of bacteria starts to get to work, changing Nitrite to Nitrate which, although still not good, is less harmful to your Fish and can be kept in check with regular water-changes, which we'll talk about later.

Plants will also help to absorb Nitrates.


So, once this ‘Cycling’ process is complete your tank is almost ready to accept some of its fish, but here we must step back and explain the Cycling a little more, the Ammonia starts to build up as a result of Fishes’ excretion which starts to rot down in the water.

So we have to kick-start this by one of two simple methods (there are other ways which involve using household Ammonia but are not recommended for newcomers as it can be very dangerous stuff).

Route one is to do it with a ‘Fishless’ method which involves daily addition of a small amount of Fish Food which will gradually break down, causing an Ammonia build-up.

The other way is to use a couple (or more, but this really depends upon the amount of water volume) of what are known to be ‘hardier’ Fish.

These are lightly fed and their ‘waste’ will have the same effect as the food in the method we mentioned before.

The preferred method is as fishless cycle so that no fish are stressed in the cycling process.


To monitor the progress of the tank during cycling Ammonia, Nitrite and Nitrate need to be measured; all can be tested by using a Water Testing Kit, an essential purchase before you buy any fish.

Firstly you test for Ammonia which will start to rise quite quickly in the first few days of the cycle and then level off and then begin to drop.

This will be the time to start testing for Nitrites which will rise as the first type of bacteria in the filter gets to work.

Over time the Nitrites too will rise, then even out as the second sort of filter bacteria start doing their job turning the Nitrites into Nitrates, now’s the time to start deciding which Fish you would like to start stocking your Aquarium with…but only decide, still don’t get rash and buy anything as you have to get the Nitrates lower still and become stable – but you are on the last leg now.


As mentioned earlier Nitrates are partially dealt with by the plants but you still need to reduce them further by removing 15-20% of tank water once a week, replacing it with the equivalent of fresh water, treated with Water Conditioner and warmed to near the tank temperature with some heated water (use the water from a boiled kettle to bring the new stuff up to near the tank's water temperature).


There are other things to be thinking about – but that, more or less, is a simplified explanation of what you will need to do before you can start adding your Fish to the Tank.


Your stocking levels must be built up gradually over a period of weeks as more fish equals more waste and the bacteria levels will only grow to the amounts of feed (fish waste) available to them, but as we have seen already, they need time to build up their numbers, if too much Ammonia suddenly builds up it creates an overload which cannot be dealt with and creates what is known as an ‘Ammonia Spike’…the whole process crashes and has to start over again, which defeats the object of the ‘Cycling’ in the first place, not to mention the possible and likely disastrous effect it will have on your Fish.

So, easy does it.


A couple of afterthoughts, your filter must be on twenty-four hours a day, but they are very economical on electricity and quiet.

Your heater will be fitted with a thermostat which only operates the heating element until the water reaches a pre-set temperature.

For a normal community tank the temperature should be set to 75F.

It is best to keep your aquarium light on for ten to twelve hours a day, you will need to experiment, too much light will lead to the build-up of too much algae.


It is very important that one person within the family is given the job of being the ‘Fish-Feeder’ (although this job an be taken in turns, but only one at a time) and it is made clear to the rest of the family that no more food can be given, too often others will be tempted to sprinkle in ‘just a little’ and although the fish will probably eat this too there is a limit to how much they can actually digest and gain benefit from and excess food or fish waste will put the filter under pressure to deal with the excess waste and can lead to an "Ammonia Spike" as mentioned before.

Different foods from different makers have different advice on how much is to be fed daily, follow the advice given.

Always remember that the people in your local Fish Shop are there to help and advise you, don’t hesitate to ask them any questions and join the Irish Tropical Fish Society’s internet Forum:


There are lots of experienced Fish-Keepers there who will be able to answer any questions you have.

The Forum is free and anyone can join and read the articles,join in and ask questions, but if you're reading this, you will have already discovered the Forum, so join up and join in.

You can also join the Irish Tropical Fish Society which meets once a month upstairs in Rosie O'Grady's in Harold's Cross at 8:30pm - the second Tuesday of every month.

Club membership includes a membership card which entitles you to discounts in many, if not all, aquatic shops.


We look forward to meeting you online or at a meeting in Harold's Cross.


The I.T.F.S. is a voluntary, non-profit society run by hobbyists for hobbyists.