Aquarium: which volume to choose?

What fish population for an aquarium of what size?

 

"It is a recurring question, to which there is no simple answer."

And, as always with complicated questions, there are simple dogmas, perfectly erroneous, but which allow one to pretend to have an answer!

As a young aquarist (so long ago!), I learned, like everyone else, THE rule: "one centimeter of fish for one liter".

"She has a few variants, such as subtracting the volume of the substrate from the water volume calculation and allowing a margin for the fill level, but overall, it is the only clear rule that is imposed on the beginner who asks the question."

 

Yet, it makes absolutely no sense.

Because it is based on a criterion that has no relevance: the length of the fish.

 

Indeed, the length of the fish does not determine its metabolism at all: neither its oxygen needs, nor its food needs, nor its filtration needs, nor its water purification needs, nor the volume of its waste (feces, CO2...).

What best determines an animal's metabolism is its live weight.

 

A friendly danio (the famous "zebra fish") measures 4 cm and weighs 0.5 grams.

While an average goldfish measures 10 to 15 cm for… 100 grams!

The goldfish is 3 times longer, but 200 times heavier.

And when it reaches 45 cm, once adult, it weighs 2.5 kg, which is only 11 times the length of a danio, but 5,000 times its weight!

Shall we put a 45 cm goldfish in a 45-liter aquarium?

 

In fish farming, powerful filtration and high oxygenation allow for staggering concentrations of fish. With a level of well-being that is probably disastrous.

 

The most widespread dogma in aquaristics is therefore false.
It does not even allow for an approach to any reality. It corresponds to nothing, except to the idea of the one who spread it in the first place.

 

On the contrary, if we look at the problem differently, we can try to rely on the natural conditions of the species.
"For a territorial fish, whether bottom-dwelling or highly swimming, the surface makes more sense than the volume."
But above all, a fish in the wild has several cubic meters of water all to itself. The natural population density is very low, there are thousands of liters per fish.

And that is not feasible in your living room!

 

"We will therefore have to make a compromise."

"Between the ideal of 10,000 liters per guppy and the obvious constraint of the square meters of our apartments."

"My dream, never realized, was an infinitely long aquarium, not necessarily deep, that would house fish in the manner of a riverbed, whose sections are alternately planted, free, sandy, or deep, dark then bright. Populated, above all, by very small species."

In short, an aquarium so long for the fish to traverse, compared to its size, that it almost forgets its captivity.

 

Some have solved this with shrimp maintenance, which swim little and spend their lives in a small space. It's a solution.

 

 

Others (and you are increasingly numerous here), have created fishless aquariums, hosting all possible critters, from exciting microfauna to snails, including the Blackworm and the water lice!
Aquatic gardens providing the living room with soft light, where something is always happening, and where size matters little, since its inhabitants are tiny!