Choosing Fish for your New Aquarium

So you’ve decided to set up an aquarium. Of the many tasks and decisions that now lay in front of you, perhaps the most important is which fish are you going to put in your tank.  There are many things to consider, but we’ll attempt to break it down to the most important and most basic questions to make it as simple as possible to help you choose fish for your new aquarium.

What Do You Like?

So what do you like? This is the most important question. There’s no point in getting a fish that you aren’t interested in.  There are lots of different species of freshwater fish with many different and unique colors with just as many different temperaments and quirks.  Perhaps you like look of an active schooling fish like zebra danios.  Or maybe you’re more interested in a tall and peaceful angelfish.  Maybe you love seeing a school of cory catfish scurrying across the substrates as it eats.

Quartermass [public work]
Quartermass [public work]
If you aren’t really sure what you like, spend some time on youtube looking at different fish.  And do some research.  There are many forums on aquariums and fish with millions of active participants.  Do some reading and see what other people are into.

I personally love a tank with lots of smaller schooling fish reaching as many different colors as possible with a nice centerpiece fish.

You can also go to a local fish store or pet store and just browse.

Do the Fish You Like Get Along?

Once you know what you like, you need to make sure your plans will work and will get along. Many fish have lots of different personalities and temperaments that don’t always work with each other and many fish have different water requirements.

Many of the most popular freshwater fish are peaceful and will do well in community tanks.  In general, tetras, barbs, rasboras, guppies, platies, swordtails, and cory catfish will all do well with most fish (Note that there are a few exceptions so do research on your particular strain). All of these fish are relatively peaceful, hardy, and have similar water requirements.

When you start getting into larger fish such as loaches and angelfish, you can run into some issues.  Loaches are typically peaceful, but they can be a bit aggressive at times.  While angelfish are often victims of nipping fish.  Their long fins, while making them beautiful, are also perfect targets.

Freshwater sharks are awesome fish, but most of them come with some pent up aggression towards their own kind.  Rainbow sharks and red tail sharks both will not tolerate two members of their own species in the tank.  Additionally, they will fight between the two species.

Bala sharks are peaceful, but can incite aggression in other similar sized freshwater sharks.

By Gogo78 [CC BY-SA 3.0]
By Gogo78 [CC BY-SA 3.0]

How Big is Your Aquarium?

It’s not healthy or safe to overstock a tank.  The rule of thumb is 1 inch of full grown, adult fish to 1 gallon of water.  So a 10 gallon should have no more than 10 inches of fish.  This is obviously just a starting point and exceptions exist in both directions.  It may be possible to keep a few more fish than the rule of thumb suggests if all fish are skinny.  On the other end of the spectrum, keeping a 40” long redtail catfish in a 20 gallon aquarium just isn’t feasible because the fish won’t be able to move. Nonetheless, this is a good starting point.

The other part of the equation is the surface area of the tank.  A larger surface area (and a resulting larger area at the bottom of the tank) typically allow a bit more fish for an aquarium of equivalent size.  So you should be able to keep a few more fish in a 20 gallon long than in a standard 20 gallon.

To check if your aquarium is overstocked, check out this amazing calculator checking bio load vs filtration vs aquarium size.