Advanced freshwater fish

Every fish here is marked difficult, and the reason is on its profile. Some need water most tap cannot provide: soft, acidic blackwater at a pH of 4 to 6 for the wild bettas and licorice gouramis, or cool, fast, oxygen-rich water for the hillstream loaches. Some refuse dry food: the pipefish, elephantnoses and pencilfish eat live or frozen food or nothing. Some need a tank built around them, a river tank, a blackwater tank or a sand bed. And all of them punish the swings of a new tank, which is why the list suits keepers with a few stable tanks behind them.

1. 01

   Water first

   Soft and acidic, or cool and fast, and always stable

2. 02

   Live food

   Pipefish, elephantnoses and pencilfish refuse flake

3. 03

   A tank built around them

   River, blackwater or sand

4. 04

   Stable tanks first

   They punish the swings a new tank goes through

The wine-red betta is a 1.4 inch (3.5 cm) wild betta for 11 gallons (40 liters) at a pH from 4 to 6, and Brown's betta is its cousin at 1.2 inches (3 cm) for the same water. The crossband chocolate gourami is 1.8 inches (4.5 cm) for 16 gallons (60 liters) at 79–86°F (26–30°C), a mouthbrooder that needs a group of six. The sharpnose chocolate gourami is the larger one at 2.8 inches (7 cm) for 24 gallons (90 liters). Elizabeth's dwarf cichlid is an Apistogramma for a pH from 4 to 6, 2 inches (5 cm) for 20 gallons (75 liters). The tucano tetra is 0.8 inches (2 cm) of blackwater schooler at a pH from 4.5 to 6. All of them want reverse osmosis water and leaf litter.

The ornate-tail Borneo sucker is 3.3 inches (8.4 cm) for 24 gallons (90 liters) at 68–77°F (20–25°C), a flat fish that grips stone in a current. The showy hillstream loach is a Sewellia at 2.6 inches (6.5 cm) for 68–75°F (20–24°C). The Stiphodon gobies graze biofilm off rock: the elegant algae goby is 2 inches (5 cm) for 14 gallons (54 liters), the orange fin goby 2.2 inches (5.5 cm) and the easiest of them to feed. The panda loach is 2.8 inches (7 cm) for 20 gallons (75 liters) at 64–75°F (18–24°C). The banded darter is a North American native at 3.1 inches (7.8 cm) for 59–70°F (15–21°C), cool enough to need a chiller in summer. All of them want a powerhead, oxygen and a mature tank with algae on the stone.

Dora's pipefish is 7.1 inches (18 cm) for 30 gallons (112 liters) and hunts tiny live prey in a calm, mature tank. The elephant baby whale is a 3.9 inch (10 cm) mormyrid for 29 gallons (110 liters) that eats worms at night. The red-tail dwarf puffer is 1.8 inches (4.5 cm) for 17 gallons (65 liters), marked peaceful, and eats snails and frozen food. The Amazon puffer is the puffer that lives in a group, 4.7 inches (12 cm) for 26 gallons (100 liters), with teeth that need hard food. The twig catfish is 5.9 inches (15 cm) for 30 gallons (115 liters), marked peaceful, and grazes biofilm that a new tank does not have. The green farlowella is its smaller relative at 2.8 inches (7 cm).

The yellow sand cichlid is a Tanganyikan Xenotilapia at 3.5 inches (9 cm) for 53 gallons (200 liters) at a pH from 7.8 to 9, kept in a group of six on sand. The cupid cichlid is a peaceful eartheater at 4.7 inches (12 cm) for 53 gallons (200 liters). The threespot eartheater reaches 9.8 inches (25 cm), lists 119 gallons (450 liters) and wants 79–86°F (26–30°C) at a pH from 4.5 to 6.5. The uaru is marked peaceful at 11.8 inches (30 cm) for 65 gallons (245 liters), kept in a group. The Heckel discus is the hardest discus at 82–88°F (28–31°C) and a pH from 5 to 6.5. The frontosa is a colony fish at 12.6 inches (32 cm) for 227 gallons (860 liters).