Temperature
Tools
- Heater (for tropical fish): 2–3 W per liter is recommended, with a thermostat
- Aquarium fans (to lower the temperature in the summer)
- Chillers (for fish or shrimp in hot climates)
- Digital thermometer (more accurate) or strip thermometer (less reliable)
CO2 (Carbon Dioxide)
Why It Matters
- It is the primary carbon source for plants
- It reacts with KH to determine the pH
- In excess: it suffocates the fish (it competes with O₂ at the gills)
Values
| Level | Situation |
|---|---|
| <5 ppm | Deficit for plants |
| 15–30 ppm | Ideal for planted aquariums |
| >30 ppm | Area posing a risk to fish |
CO2 Indicator (Drop Checker)
Container with pH indicator liquid (blue = low CO2, green = ideal, yellow = excess). It reacts 1–2 hours later than actual water.
CO2 Injection Systems
- Liquid CO2/DIY: Sugar + yeast mixture—inexpensive but unstable
- Disposable CO2 cylinder (Dennerle Easy Carbo type): refillable, easy to use
- Pressurized CO2 cylinder + regulator + diffuser: A professional, precise, and cost-effective system in the long run
- Liquid CO2 (Easy Carbo, Excel): provides carbon through a chemical process; it is not gaseous CO2 but partially substitutes for it; also a mild biocide
Dissolved Oxygen (O2)
What is it?
O₂ dissolves into the water from the surface and is consumed by fish, bacteria, and through the cellular respiration of plants (at night).