One of the biggest mistakes that people make with tropical fish is overcrowding their tank.
It is very important to keep your tank at least slightly understocked. Having too many fish will lead to illness, fighting and even death.
As a general rule, the calculation for how many fish can go into your tank is 1 inch of adult fish per 1 gallon of water, making sure to take 10% of water off for gravel, decorations etc. Territorial species of fish will need double the space, so 1 inch of fish per 2 gallons of water.
This is just a general rule though. There are other things to take into consideration, which I will cover in this article.
Things to Consider When Calculating How Many Fish.
Water Measurement.
Depending on where in the world you are, your tank capacity will either be in gallons or litres.
In America, they use gallons.
In the UK, they use litres.
There is a BIG difference between a litre and a gallon when it comes to the size of a fish tank. 1 litre is the equivalent of 0.3 US gallons.
Substrate, plants and decorations.
As a general rule, you should take away at least 10% of the water in your calculation to account for any gravel, plants and ornaments. If you have many plants in your tank, I would up that to 15%, just to be on the safe side.
Single Species or Community Tank?
It is slightly more difficult to calculate space requirements if you have a community tank as some species of fish can be territorial so need double the amount of space.
Do your research on the different types of fish you would like to see what their temperament is like.
Size.
This is probably the most important thing to remember. You must do your calculations based on the adult size of your fish, not the size they are when you get them.
Again, do your research to find out what the average adult size of your fish species will grow to before working out how many you can add to your tank.
How Many Cichlids Can I Put into a Tank?
When it comes to adding Cichlids to your tank, there a number of things you need to consider.
Cichlids can be both territorial and aggressive. If they don’t have enough space in the tank this will not end well.
In addition to having the correct sized tank for Cichlids, you also need to make sure you have the correct shape. Cichlids need space to swim around, so need a large surface area to be able to do so. It is no good having a really tall but narrow tank as this will not give them the space they need.
It is easy to work out the surface area of a tank.
Surface area of a fish tank = length x width.
To calculate how many fish you can have using this method is:
1 inch of adult fish for every 12 square inches of water surface area. For wide bodied fish, it is 1 inch of adult fish for every 20 square inches.
The greater the surface area of your tank, the more fish you should be able to have.
Cichlids would be classed as wide bodied fish.
If your calculations don’t end up as a whole number, always round your number down to err on the side of caution.
There is a brilliant fish stocking calculator website, called aqadvisor.com where you can put in your tank dimensions, the type of filter you have, and what type of fish you want to add. This will calculate what percentage stocked you will be, as well as advise you about water change amounts and frequencies. I have found this calculator to be the most accurate and informative.
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When it comes to the Cichlid family, it’s not like Little House on the Prairie where they all get along just fine.
Some species of Cichlids will not get along at all and will constantly fight, no matter how much space they have. It is easier to have the one species of Cichlid in your tank, but even then, as they grow, you need to keep an eye out for any signs of aggression.
How Many Cichlids Can Fit in a 40, 60, 75 or 125 Gallon Tank?
You may, or may not be aware, that Cichlids come in many different shapes and sizes.
For the purpose of the table I have compiled, I have taken 3 different sized species of Cichlid:
The Golden Eye Cichlid, adult size 3 inches approx. Other examples of Cichlids that grow to the same size are:
Butterfly, Borelli’s Dwarf and Crested Dwarf.
The Rusty Cichlid, adult size 4 inches approx. Other examples of Cichlids that grow to this size are:
Agassiz’s Dwarf, Eyespot Krib, Malawi Golden, Blue Peacock and Lemon Cichlid.
The Convict Cichlid, adult size 6 inches approx. Other examples of Cichlids that grow to this size are:
Keyhole, Lifalili and Eduard’s Mbuna.
There are some species of Cichlid that grow a lot larger, for example:
Jack Dempsey (8 inches)
Pearl Cichlid (11 inches)
Midas Cichlid (12 inches)
Frontosa Cichlid (15 inches)
For the purpose of international peacekeeping, I have compiled information for both gallons and litres.
I would use these tables as a rule of thumb. I would always suggest you double check with aqadvisor.com to be doubly certain.
Cichlid Calculator in Gallons.
| Gallon | Minus 10% | Golden Eye Cichlid (3 inch) | Rusty Cichlid (4 inch) | Convict Cichlid (6 inch) |
|---|---|---|---|---|
| 25 | 22 | 4 | 3 | 2 |
| 40 | 36 | 6 | 4 | 3 |
| 50 | 45 | 6 | 4 | 3 |
| 60 | 54 | 8 | 6 | 4 |
| 75 | 67 | 10 | 8 | 5 |
| 90 | 81 | 12 | 10 | 6 |
| 125 | 112 | 18 | 14 | 9 |
| 150 | 135 | 22 | 16 | 10 |
How Many Cichlids Will Fit in a 60, 80, 100 or 140 Litre Tank?
Cichlid Calculator in Litres
| Litre | Minus 10% | Golden Eye Cichlid (3 inch) | Rusty Cichlid (4 inch) | Convict Cichlid (6 inch) |
|---|---|---|---|---|
| 25 | 22 | 0 | 0 | 0 |
| 60 | 54 | 2 | 2 | 2 |
| 70 | 63 | 2 | 2 | 2 |
| 80 | 72 | 3 | 2 | 2 |
| 100 | 90 | 3 | 2 | 3 |
| 140 | 126 | 5 | 4 | 3 |
