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9 Step Guide to Setting up Your Aquarium


Freshly Planted Aquarium

Once you have bought your aquarium you get to enjoy the first fun part which is setting it up.

How do you go about setting up your aquarium? The following list will give you a running order:

  1. Siting your aquarium
  2. Preparing your ballast
  3. Hard water or soft water?
  4. Filling your aquarium
  5. Fitting your heaters
  6. Powering up
  7. Preparing your plants and stones
  8. Adding your plants
  9. Before you introduce fish

1. Siting your aquarium

Let’s make an assumption that you have a twenty-gallon, glass aquarium to set up. Such a tank is likely to be around L24″ X D12″ X H16″, or thereabouts. A good quality, glass tank of this size will weigh in the order of 25 pounds empty.

Before you site it anywhere you need to know how much it will weigh once you fill it with water. We’ll keep the math simple so that approximate calculations will be easy to calculate. Let’s assume that one gallon of water weighs around 10lbs because it’s best to err on the heavy side. Twenty gallons of water will weigh in at around 200lbs. Add the weight of the tank itself and you have around 225lbs.

Bear in mind that a twenty-gallon tank is ideal for a first tank but in the world of aquariums, it is quite a small tank. Even so, wherever you site your tank, the location must be comfortably able to carry the 225-pound load without issue.

Be careful about siting your aquarium in direct sunlight, especially if the light is coming from a south-facing window (in the northern hemisphere). In such a position, your tank will get direct sunlight throughout the day.

It is often the case that you will want to attach either a neutral (e.g. green) background paper or a suitable, aquatic image to the back of the aquarium to give it that final touch of class. There is also no reason not to add suitable “backgrounds” to the sides as well, especially if the tank is to be enclosed behind a decorative panel, as is often the case.

You may wish to consider adding polystyrene or foam insulation to the back and sides unless this will make the tank unsightly because, in the event of a heater failure, the gradual loss of temperature from the water will be slowed down quite markedly.

In siting your tank you should give careful thought to where you will place electrical systems such as power blocks, the pump(s) and other related equipment such that they don’t look unsightly.

I have always favoured under-gravel filters in my aquariums because they remove any toxins that work their way down through the gravel. Check out my article on filter systems to determine which solution you prefer. If you elect to use an under-gravel filter, this will need to be fully installed before you add any gravel, as once it is installed it is a permanent feature of your aquarium. For a twenty-gallon tank, my recommendation would be to have lift tubes at the left and right, rear corners.

Installing an under-gravel filter

2. Preparing your ballast

I prefer my aquarium to look as natural as possible, with gravel and some well-chosen rocks at the bottom and living plants. Your choices may be different but the preparations you need to take are the same.

When your gravel is finally installed in your tank it needs to be one to two inches deep at the front sloping up to around five inches at the rear. You can add rocks (if desired) when you add the plants, later on.

Before putting anything into your aquarium it is important to ensure that it is clean and dust-free. Any kind of gravel that you choose will probably be shipped in a bag of some kind and during transit, the individual pieces will rub together and some dust will always be included (free-of-charge!). You don’t want the dust so you will need to wash that off before the gravel goes into the aquarium.

Washing off unwanted dust can take some time so be patient. Don’t try to clean all of the gravel at once, do it a little at a time. Your objective is to remove fine particles of dust by gently washing the gravel under running water in a container until that batch of gravel is free from dust. Once free from dust that gravel can be added to your tank.

Repeat the process until all of the gravel has been cleaned and is in the tank.

Under no circumstances use any form of detergent to wash the gravel, as this may prove fatal to your fishes.

3. Hard water or soft water?

Dependent upon where you live, your tap water could be very hard (with lots of limescale) or it may be quite soft (with little to no limescale).

Soft water is most certainly the best for your fishes and your plants.

I would recommend using a water filter (such as a Brita filter) to prepare the water that you are going to add to your aquarium. Irrespective of the amount of limescale in your water there may be other impurities that a human can tolerate but that a tropical fish cannot so investing in a Brita type water filter is a sound investment.

Before adding any water to your tank, place a sheet of unbleached paper over your gravel so than you slowly pour (or syphon) the water onto the paper. This avoids disturbing the gravel and any sediment that may still be within it.

4. Filling your aquarium

Filling your aquarium should be done slowly, using soft, filtered water. This is going to take a while so you should be patient.

In fact, this is good practice for when you periodically top-up your tank.

I recommend that you adopt the syphon method using a length of air pump hose, which is very narrow and therefore will gently and slowly fill the tank. If you are using a Brita filter jug (or similar), decant the filtered water into another clean container and syphon in the water from there. This will enable you to filter the next batch of water and add it to your header tank for syphoning.

You need to add sufficient water to cover your heaters and thermostats and I recommend that these should be placed vertically (see next section) so that means that your tank will be almost or completely filled.

5. Fitting your heaters

By default, if I am heating an aquarium I use two separate heating systems to mitigate the risks of heater and/or thermostat failure so for the purposes of heating a twenty-gallon tank I use two heaters and thermostats each suitable for a ten-gallon tank.

My rule of thumb is that to raise one gallon of water by five degrees Fahrenheit above the surrounding room temperature requires two watts of power. The desired temperature for your aquarium is 75 degrees Fahrenheit. Subtract your room temperature from 75 to establish by how much you need to raise the water temperature in your tank.

Let’s assume that your room temperature is 70 degrees Fahrenheit. You need to raise the temperature by five degrees. In total, this will require 40-watts of power in a 20-gallon tank so you will need two, 20-watt heaters to raise the water temperature and maintain it at the desired temperature.

Murphy’s law states that anything that can go wrong will go wrong. This being true, assume that your thermostats will both fail in the “on” position. By having only sufficient heating power to maintain your tanks at the desired temperature you cannot cook your fishes in the worst-case scenario. If one thermostat fails in the “on” position and the temperature goes above the setting for the second heater thermostat then that heater will not come on. By dividing the heating task to separate heaters and thermostats, both of which are required to maintain the required temperature then the risk of cooking your fishes is all but eliminated.

Always have a spare pair of heaters and thermostats available. Again, assume Murphy’s law. Heaters and thermostats only cost a few dollars so investing in a spare pair is a sound investment. In any event, I would install new heaters and thermostats annually to be safe.

Add a digital thermometer sticker to the front left or right side so that you can check the temperature at least once per day.

I recommend fitting your heaters vertically, at the back of the tank, one on the left side and one on the right side. If you are using an under-gravel filter then place them about an inch away from the lifter tubes so that the water circulation immediately starts to move the heated water around the tank.

Aquarium heaters and thermostats.

6. Powering up

Now that your tank is filled with water, it’s time to power it up.

Ensure that your heater thermostats are both set to 75-degrees Fahrenheit. Your initial objectives are to filter the water whilst heating it up to the desired temperature.

If you have an under-gravel filter then it is already fitted. Just ensure that the carbon filters are attached and that you have a replacement set of filters to hand.

If you are fitting an internal or external filter then do so now, as the filters will constantly circulate the water and clean-up any residual dust that may exist in the gravel.

Once your aquarium water is clear and the correct temperature is being maintained then it is time to start to introduce plants.

7. Preparing your plants and stones

Assuming that you are adding live plants to your aquarium, now is the time to start adding them.

With a 20-gallon tank, you have plenty of scope for adding plants. I tend to add oxygenating plants in rows in order to create corridors inside the tank behind which the fishes may swim.

Coming from a part of the country which had really soft water and 19th-century plumbing, I have always tended to use thin strips of lead to anchor plants in small clumps.

Using lead has rather gone out of fashion (though you can still buy lead strips that are not made of lead) so the following video provides one (of many) other methods of anchoring your plants in your gravel:

I tend to bring more decorative plants towards the front corners of the tank so that they can be seen in all of their splendid glory.

For smaller fishes, it is useful to include hideaways by adding clusters of stones in such a way that the smaller fishes can hide amongst them safe from the attention of larger fishes. Fishes love to eat fish and even a mother will eat its own offspring so your plants and rocks should be prepared with this in mind.

8. Adding your plants

Add your plants by inserting them well into the gravel and so that they are anchored down, as described above.

Plant corridors along which fishes can swing and clusters in which smaller fishes can hide from predation.

When you have added your plants, give your tank a day or so to settle and then add some fish food. You don’t need much – your intention is to start the natural cycle of growth and decay into your tank. Just a sprinkling of food will gradually sink to the bottom of the tank and start to decay in the gravel. Your plants will start to pick up any nutrients in the water and your filter system will remove any unwanted chemicals.

9. Before you introduce fish

There are many and varied opinions as to how long a freshly planted aquarium should be left before you introduce fishes to your tank, varying from one week to two months.

In my experience, I have found that by adding a pinch of fish food each day, the decay and growth cycle is kickstarted such that I have been able to introduce fishes after one to two weeks.

As soon as you introduce fishes, their natural cycles will further enhance the chemistry of the aquarium.

I have left lighting an aquarium thus far because there are many forms of lighting from which to choose. Whilst you can purchase LED lights that give an array of coloured lights to your aquarium, despite the fact that this may look attractive I would prefer my fishes and plants to live in a world of natural light. For this reason, I use lights that simulate natural daylight.

Try to give your fishes and plants as natural an environment as possible and they will thrive. Too much light will encourage the growth of algae and you will forever be cleaning your tank glass. Too little light and your plants will suffer and the water chemistry will deteriorate.

If your tank is behind a housing then the lighting rig may be just a light on the wall above the tank. If your tank is fully in view than you may elect to place a light hood over the tank with the light inside.

To lessen evaporation, you may also add a layer of clear acrylic material over the top of the tank ensuring that there is a gap between the acrylic and the water to ensure that fresh air can circulate over the surface of the water. If you have a light hood over the tank, ensure that there is ventilation in the hood for fresh air to circulate.

At the end of the first week, replace the filter material in your tank filter because it will have collected pretty well all of the unwanted material from the tank (suspended dust particles, etc.). Your tank should be crystal clear now so from this point just change the filters at least as regularly as recommended by the manufacturer.

Setting up your aquarium – Video

Mike Wheeler

I started keeping freshwater tropical fish in 1972 and it has been something of a passion ever since. In this website, my aim is to build up an everyman's guide to help the everyday aquarist get the best from this inspiring and entertaining hobby.

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