The tank and where to put it
Get the largest tank you can set up, bearing in mind the adult size of the fish. A large volume of water is more stable: temperature, pH and waste change more slowly than in a small tank. For the same volume, a wide, shallow tank offers more surface for oxygen exchange than a tall one.
- Away from direct sunlight, radiators and draughts, which make the temperature swing and encourage algae.
- On a level, sturdy stand designed for the weight of the full tank: a litre of water weighs a kilo, not counting the glass, substrate and decor.
- Away from noise, vibration and busy walkways, and within reach of a socket and a tap for maintenance.
Filter flow
360 to 600 L/h
3 to 5 times the volume per hour (Tropica), a little more for heavy eaters.
Heater
100 W
Guideline from the manufacturer EHEIM; allow more if the room is cold.
Lighting
1,200 to 2,400 lm
10 to 20 lumens per litre for easy plants, 2,400 to 4,800 lm for “Medium” plants (Tropica).
Lighting period
6 h, then 8 to 10 h
6 hours a day for the first two to three weeks, then 8 to 10 hours (Tropica).
Weekly water change
12 to 30 L
10 to 25% of the volume every week (OATA).
Weight of the water alone
120 kg
A litre of water weighs a kilo: add the glass, substrate and decor when choosing the stand.
Heating and temperature
Most tropical fish live between 24 and 28 °C; each species’ range is given on its profile. A thermostatic heater, placed near the filter outlet to spread the heat, keeps the water at this temperature. Check it with a separate thermometer, in case the thermostat fails.
| Power | Recommended volume |
|---|---|
| 25 W | 20 to 25 L |
| 50 W | 25 to 60 L |
| 75 W | 60 to 100 L |
| 100 W | 100 to 150 L |
| 150 W | 200 to 300 L |
| 200 W | 300 to 400 L |
Oxygen and water movement
Oxygen enters the water through the surface: the more it is agitated, the faster the exchange. Yet the amount of oxygen water can hold falls as it warms up. At 25 °C, saturated water holds only 8.3 mg/L.
Fish that stay at the surface with their mouths open are short of oxygen. Point the filter outlet towards the surface so that it ripples, or add an air stone connected to a small pump.
Filtration
The filter moves the water, traps particles and above all houses the bacteria of the nitrogen cycle. No fish should live without a well-maintained filter. The water usually passes through several layers:
Mechanical
sponge, filter wool
Traps particles. Rinse as soon as the flow drops.
Biological
ceramic, coarse sponge
Houses the bacteria. Rinse only in tank water.
Chemical
optional: activated carbon
Removes dyes and traces of medication. Gets used up, replace it.
| Filter type | For which tank | Good to know |
|---|---|---|
| Internal | Small and medium tanks | Cheap, but takes up space in the tank |
| External (canister) | Medium to large tanks | Plenty of room for filter media, quiet, hidden in the stand |
| Hang-on-back | Small and medium tanks | Easy to maintain; agitates the surface well |
| Sponge and air pump | Small tanks, fry, shrimp | Gentle current, does not suck in small animals |
Tropica advises a flow of 3 to 5 times the tank volume per hour: 450 to 750 L/h for 150 litres. The flow stated on the box is measured without filter media; the real flow is lower. Small or long-finned fish, such as the betta, prefer a gentle current.
Lighting
Light is for the plants and for our enjoyment; the fish mainly need a regular day and night rhythm. To compare lights, Tropica advises looking at lumens rather than watts: 10 to 20 lumens per litre are enough for easy plants, 20 to 40 for “Medium” plants, and over 40 for the most demanding.
In a new tank, Tropica recommends 6 hours of light a day for the first two to three weeks, then 8 to 10 hours. A timer plug keeps the schedule constant.
The starter list
The tank
- Glass or acrylic aquarium
- Stand built for the weight
- Lid
The equipment
- Filter
- Thermostatic heater and thermometer
- Lighting (essential for plants)
Maintenance
- Water conditioner
- Tests: ammonia, nitrite, nitrate, pH and hardness
- Gravel siphon and a bucket kept for the tank
The substrate, plants and decor are covered in the next lesson.
Key points
- A large tank is more stable than a small one: plan for the adult size of the fish.
- Allow a filter flow of 3 to 5 times the volume per hour and a heater suited to the volume.
- Warm water holds less oxygen: agitate the surface, especially in summer.
- Start with 6 hours of light a day, then 8 to 10 hours once the tank is established.
Sources
- OATA, “How to set up and look after a freshwater tank”
- RSPCA, “Fish environment”
- USGS, “Dissolved Oxygen” (solubility tables)
- OATA, “Water quality criteria”
- EHEIM thermocontrol, power by volume (product page)
- Tropica, “Water circulation”
- Tropica, “The right light for your aquarium”
- Tropica, “Starting a new aquarium”
Written by Aquarius from these sources. They do not replace a vet's advice.