How to Set Up a Perfect Freshwater Aquarium

Updated on August 14, 2019
Ko-Dan Armada profile image

I love my freshwater aquarium, and I like sharing tips on how to build and set one up.

New Aquarium Purchase?

You went to the pet store and purchased the perfect 10-gallon aquarium kit, which probably included the tank, filter system, heater, aquarium top, light, net, and your first water conditioner sample. You purchased some gravel, a few fake plants, and a really cute decoration for the centerpiece. You have read all the instructions for adding the water conditioner to the tap water, and now the tank is up and running. You're ready to add the ten new fish. You float the bagged fish in the new tank water for fifteen to twenty minutes, because that is what the salesperson said to do.

So everything looks great. Everyone that comes into the room comments on how cool your new tank looks. Then after about a week or so you notice a few dead fish, and you think that's strange, they must have been sick when I bought them. You go back to the store and get some more, but a few days later all your fish are dead.

You just experienced what happens to most with their first tank. It happened to me—more than once, I hate to admit. What happened was your fish suffocated in their own bodily fluids and decayed food. Fish poop and decayed food create deadly ammonia.

Dead Fish?!?

Don't worry, it happens to almost everyone.

What Went Wrong?

Don't panic, and don't feel bad, as this is all normal. Probably the only problem was adding too many fish. Ammonia levels increased to the point that they could no longer breathe. It's kind of harsh, but it was like swimming and breathing in an unflushed toilet. Water quality and beneficial bacteria are the secrets to keeping your fish alive and having a clean-looking tank.

Proper Setup of a Freshwater Aquarium

It usually takes about six weeks for an aquarium to get balanced (attain the proper amount of beneficial bacteria to support fish life).

So for the first six weeks or so, you should do water changes weekly. Most fish keepers would recommend regular water changes of about 10 to 20 percent of the tank water every two weeks. However, because the ammonia levels are going to be pretty high for the next three to four weeks of the cycle, it is recommended to do these water changes weekly to reduce the ammonia levels so the fish will not die.

The store will tell you they have chemicals that will reduce or remove the ammonia from your tank. However, in order for the beneficial bacteria to populate in your tank, there must be ammonia present. So by removing the ammonia chemically, you are slowing or completely stopping the growth of this needed and sought-after bacteria.

So just stick with the weekly water changes. There are products that are supposed to speed up the growth of the bacteria, such as the "Ecologic Microbe Special Blend," but the time I tried this solution, I didn't notice that my tank cycled any quicker. So I have not used these products again. However, I have friends that swears by them and has told me time and time again they can cycle a tank in three weeks. Anyway, it's up to you, they can't hurt I guess, but they are a little expensive.

Cycling a Fish Tank

Aquariums must be cycled before you add all the fish.

Checking Water Quality

During this initial six-week setup process, it is a good idea to check your water.

Most pet stores will do water checks for free. Petco and Petsmart both advertise free water testing.

Or you can also purchase your own kit. The six basic tests for a freshwater aquarium include:

  • Ammonia
  • Nitrite
  • Nitrate
  • Water Hardness
  • Alkalinity
  • PH

There are two basic kinds of aquarium water test kits:

  • The first has dry strips that, when dipped into your aquarium water, change color. Then the color is matched to a chart that will give the test results.
  • The second type has drops. This liquid kit comes with little test tubes which hold the tank water. Drops are placed in the test tube and again, the color change is matched to a chart for test results.

The liquid drops are more accurate, but also more expensive. I usually I just go to Petco by my house and have the salesperson check my water, but you should be very careful because not all salespeople are created equally and some have no clue what they're doing, so make sure they show you the results as they compare to the chart. That way, you can draw your own conclusions.


Back to Water Quality and the Nitrogen Cycle

Ammonia is the first element that will appear in your tank, and as stated earlier, it comes from your fish using your tank as a toilet and from decaying food.

Once the ammonia is present in the tank, a bacteria will begin to grow, consume the ammonia, and convert it to a less harmful byproduct know as nitrite. Again once the nitrite is present, another bacteria will grow that will eliminate the nitrites and convert it into nitrates. Low levels of nitrate are harmless to your aquatic life, but as time goes on, your bacteria will continue to convert ammonia and nitrites, so the levels of nitrate will become dangerously high. This is where the bi-weekly water changes come into play.

As a side note, only feed your fish once per day during this initial six-week setup, and only feed them as much as they will eat within a two to three minutes period. Excess food will increase ammonia levels higher than they need to be.


Feed your fish only once a day, only as much as they can eat in two or three minutes.

Changing the Tank Water

Water changes not only remove nitrates and ammonia during the initial setup, but they also help oxygenate the water. Your system filter and air bubble system moves the water around in the tank, which allows oxygen to enter the water. This same movement also discharges carbon dioxide. However, over time, the water properties break down, and the water's ability to hold oxygen and release carbon dioxide decreases. So adding fresh water during your bi-weekly water changes greatly helps with oxygen levels in your tank, which makes breathing easier for your fish.

Air systems are not required for aquariums, but they do help with the movement of water, and also create a cool visual aspect to the tank.

During this vital six week cycle period, don't replace your filtration filter media. If it looks dirty or filled with leftover food, simply rinse it out in the tank water, you removed during the water change. Chlorine from tap water will kill the bacteria growing on the filter media, so lightly rinse in tank water. The filter is the first place the bacteria will begin to grow.

Once you have maintained your tank with two or three fish living and doing well for about four weeks, it is time to test the water. The ideal situation is that you will notice that all the ammonia is gone from the tank and you now see nitrites. Or even better, all you see is nitrate. If all you see is low levels of nitrate, then it is time to add new fish, but remember to add them slowly, two or three at a time, waiting at least a week between each new batch.

Then just do regular bi-weekly or preferably weekly water changes. Regular water changes also help to maintain proper PH levels. Stay away from PH additives.

Too many fish in your fish tank.
Too many fish in your fish tank. | Source

How Many Fish Can I Have?

Most fish-keepers recommend having one inch of fish per gallon in your freshwater tank. This should be based on the adult size of the fish, so for a ten-gallon aquarium, the max load would be about ten one-inch fish, or five two-inch fish, and so on. There are very few tropical types never grow larger than one inch, so you will probably want to stay with the two to three-inch fish.

Overstocking will create major problems with ammonia and water quality. The amount of beneficial bacteria a tank can populate is based on the size of the tank.

© 2011 Ko-Dan Armada


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