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Choosing Freshwater Aquarium Fish

“Let’s talk about fish, baby…”

The size of my tropical freshwater aquarium fish is pretty much dictated by the location and the space available.
But more about that later.
For now I have a rough idea of the size so I need to consider what freshwater aquarium fish I can keep.

Too many things to consider.

What do I want? More importantly what do the freshwater aquarium fish want?

My wants:

The installation needs to be:

  • Interesting
  • Soothing
  • Easy to maintain

The freshwater aquarium fish want:

  • The water chemistry needs to be right
  • The water quality needs to be right
  • The environment needs to be right
  • My companions need to be compatible

I’ve already discussed the water chemistry and quality.

The environment needs to replicate the conditions the fish would live in if they were free and wild.
I need to consider the type of substrate, whether the fish prefer rocky terrain or one with many plants.

Do the fish seek shelter?

And what fish can live together in a relatively confined space: Are they slow moving? Skittish? Do they eat the plants? Do they eat each other? Are they aggressive?

General Community Aquarium

A General Community Aquarium is a basic set up.
The fish in a general community aquarium can survive in a variety of conditions:

  • Variations in water chemistry
  • Tolerant of occasional mishaps in water quality
  • Not too fussed with the decor
  • Will eat any synthetic fish food

But there is still the big questions – are the fish suitable? Are they compatible?

Tropical Freshwater Fish Size

Are the fish fully grown or will they outgrow the tank?
Can the little fish swim together with the large fish without accidental injury
Can the little fish swim together with the large fish without getting eaten?


Are the fish omnivores (will eat animals) or piscivores (will eat only fish)
Are the fish ‘fin-nippers’, taking chunks out of the fins of other fish. Do the other fish have long fins??


Do the fish originate from turbulent waters or slow moving less agitated waters?
Fish from turbulent waters could possibly survive in well oxygenated calm water but sail-finned species evolved to glide through calm waters will not make it in a strong current.

Tropical freshwater fish from the rainforest will use vegetation to shelter. There will be roots and dead branches to hide in.
Mangrove swamps are similar to the rainforest except the water chemistry is much different.
Fish from the rapids live in crevices in the rocks and under boulders. Not much vegetation here.

Providing enough cover of the right size and shape is very important especially for the small fish who are at the bottom of the food chain and will be stressed out if they have nowhere to run and hide.

Dietary Considerations

Fish with special food needs are better avoided for the moment.
Worms and mosquito larvae may not be available and feeding live fish to a piscivore may be distasteful.
Herbivores may not eat the small fry but will decimate my underwater garden.

Size Matters

Tropical freshwater fish living in an aquarium is not natural for the fish so I need to make it as pleasant as possible for them. The biggest constraint is the size of the tank versus the size of the fish in it.

Some species need privacy. And they may fight for the right.

Territorial species need to have enough space for themselves with enough room in the tank for their neighbours.

Many species enjoy the safety in numbers provided by a shoal so keeping just one or two of this fish type is also destined for failure.

The number and size of fish that a freshwater fish aquarium can accommodate is calculated by the total length of all the fish relative to the surface area of the aquarium.

And its all about the oxygen availability at the surface of the water.

For tropical freshwater fish I need to allow 200 sq cm of surface area for each 2.5 cm of fish.


  • What fish would I like to keep
  • How big do these fish grow
  • Do I have enough space to fit the aquarium in
  • Can I provide the right water chemistry
  • Do the fish eat plants
  • Will they vandalise the decor
  • What decor do these fish need
  • Will the different species live happily together
  • How many and what species can I accommodate in my size of fish tank
  • Can I afford to feed them (Any special dietary needs)
  • Do I want to breed the fish

Next up, I look at the equipment I will need…


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