Where Do I Begin? – The Basics of Starting a Freshwater Aquarium

So you’re considering getting some fish? A brand new pet perhaps? Whilst they can be enthralling and fascinating to observe and tend to, many people are put off keeping them due to the aquarium itself. Be it the maintenance, cleaning or even just the general start up.

Gone were the days that you could win a goldfish in a fair, fill a glass bowl with tap water and put it in without any concern at all with the fishes wellbeing or the aquariums stability. Thankfully knowledge on fishkeeping has advanced significantly since then and for the better. So don’t panic!

Both Tropical and Coldwater aquariums begin with these initial steps.

1. Get the water.

If it is a brand new aquarium, rinse out any dust that may be sat in the bottom and fill with water. DO NOT USE BOTTLED WATER, IT CONTAINS MANY MINERALS THAT WILL AGGRESSIVELY EFFECT THE COMPOSITION OF YOUR WATER.


If you are using TAP WATER, which is recommended, treat with a conditioner or ‘dechlorinator‘ such as API’s Tap Water Conditioner or Tetra’s Aquasafe. This treatment will remove CHLORINE and many heavy metals in tap water as well as other materials such as silicates. In the long term, this means that life, in the form of helpful bacteria (think Yakult) can flourish in your aquarium.

Add any substrate into your aquarium at this point (gravel, sand, stones etc). For more information on substrate and what is suitable in an aquarium click here.

Remember: Life hates chlorine.

At this stage it is also advised to have your filter or pump running to ensure that the majority of chlorine is treated.

2. Get Bacteria.

Now your water has been treated, and the CHLORINE has been dealt with, you can now introduce friendly bacteria to your aquarium. This can be done via two options:

Wait 7-10 days for the bacteria to naturally culture


Add live bacteria into the water via treatment.

We’d personally recommend a mix of the two; Add some live bacteria, for example API‘s Quick Start or NT LABS’ Filter Starter, and then give your aquarium at least 5-7 days or so to settle before adding fish (the longer the better).

Slow and steady is always best approach in our book.

Remember: Always add Bacteria AFTER removing Chlorine.

3. Get it running.

Now you’ve got the bacteria you can get the rest of your kit running. If you haven’t already, get your filter running in the aquarium. This will circulate the water, oxygenating it for the fish and in the long term helps keep it clean, by mechanical and biological means.. Whether this is in the form of a Power Filter (with a built in pump) or a Sponge Filter (driven via an external air pump). External power filters are to be primed and setup at this point also.

Click here for some information regarding the Aquael ASAP Filter.

If you’re going to go for tropical, which arguably isn’t much of a change from coldwater, then now is the time to get your heater in the water, plugged in and turned on.

Many people on their first dive into fishkeeping go for coldwater first and then eventually convert the setup to tropical, by simply adding a heater.

If you are interested in setting up a coldwater aquarium but are unsure with your options in terms of fish, click here to see our guide on ‘temperate fish’.

4. Get started.

Okay, so you’re now ready to add some fish into their new environment. Due to the fact that this is a brand new ecosystem (consider how long rivers and lakes took to get going!), you still have to take it steady.Fishkeeping is no place for rushing.

You can add one or two fish now, but this is dependent on the size of your aquarium, and the type of fish that you are after.


For example, Goldfish are brilliant but messy fish. As your filter is brand new (bacterially), it might be a bit of a push to introduce a large goldfish into your tank right now. Instead, try introducing some smaller, hardy fish such as Zebra Danios that will build up the filter’s efficiency. They will produce waste also, but not nearly as much as to overwhelm the active bacteria whose job it is to digest ammonia produced by the fish.


Many other smaller fish are appropriate for these jobs, even much smaller goldfish for a coldwater aquarium and plenty of options for tropical.

After introducing your first fish, give it another week to let your aquarium accomodate the new inhabitants, and then you can look to add more.

We’d always advise getting your water parameters (ph, ammonia, nitrates etc) checked after that first week or two, to make sure that everything is going okay, ensuring that the bacteria is processing the ammonia in the aquarium.

Introducing live plants also helps the Nitrogen Cycle along, as plants will digest such toxic substances as Nitrates that are indirectly caused by fish. Plants will also contain vast amounts of bacteria to get an aquarium started.

For more information on Ammonia and the Nitrogen Cycle, click here.

New Tank Syndrome

If pre-emptive measures such as these are not taken, you will be susceptible to what is known as New Tank Syndrome. This is when the amount of fish waste products (ammonia, nitrites) are greater than the amount of active bacteria. This is why more established aquariums are more stable. Likewise, old aquariums and ponds can be taken over by Old Tank Syndrome. Essentially the opposite of New Tank Syndrome, this condition is found in bodies of water that have been left alone too much and become increasingly, yet gradually, toxic due a lack of water changes. This, along with other common issues of tank maintenance, will be discussed in later posts.

So in just 4 steps you’ve created a brand new aquarium.

  1. Introduce Water

  2. Introduce Bacteria

  3. Introduce Filter

  4. Introduce Fish

As always, we are happy to help with any queries or questions regarding the development of a Freshwater aquarium.

Feel free to contact us

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