Volume

1. Temperature: Species must share a temperature range
2. Water Hardness and pH: Do not mix fish from soft, acidic water with fish from hard, alkaline water
3. Behavior: Aggressive vs. Peaceful Fish
4. Size: The principle "if it fits in your mouth, it's food"
5. Territorial: Some fish defend areas of the aquarium
6. Swimming level: Deep, middle, surface → spread out to use the entire space

Common tank setups that work well (tropical freshwater)

• Tetra + Corydoras + Ancistrus (small pleco) + Neocaridina shrimp
• African dwarf cichlids (Apistogramma) + Nerite snails + small tetras
• Barbus + Botia + Gyrinocheilus

Common Incompatibilities

• Cold-water fish (goldfish) with tropical fish
• Large cichlids with small fish
• Male betta with another betta
• Aggressive herbivorous fish (some mojarras) and plants

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Recommended First Steps

Acclimating New Fish

Floating Bag Method:

1. Let the sealed bag float for 15–20 minutes (to equalize the temperature)
2. Open the bag and add water from the aquarium every 5 minutes for 30 minutes
3. Remove the fish with a net (do not pour the water from the bag into the aquarium)

Drip method (more accurate for shrimp and sensitive fish):

1. Place the fish in a bucket with the transport water
2. Connecting a tube to a stopcock that is leaking water from the aquarium
3. 1–2 drops per second for 1–2 hours
4. Transfer the fish using a net