Rio Negro basin, tropical South America
Black Arowana
Osteoglossum ferreirai
Temp24–30°C
pH5–6.5
Size80 cm
DietCarnivore
SwimMiddle
DifficultyExpert
Black Arowana
Osteoglossum ferreirai
fish
Soft-water fish (acidic pH range)
Species whose maximum documented pH is 6.8 or below — typical of soft, acidic setups; confirm with your own measurements.
15 species
- Asia
Chocolate gourami
Sphaerichthys osphromenoides
Temp26–31°CpH4–6.5Size5 cmDietCarnivoreSwimMiddleDifficultyModerateChocolate gourami
Sphaerichthys osphromenoides
- Peninsular Malaysia, Sumatra, Borneo
Coolie loach
Pangio semicincta
Temp21–26°CpH5.5–6.5Size10 cmDietOmnivoreSwimBottomDifficultyEasyCoolie loach
Pangio semicincta
- Asia
Dwarf rasbora
Boraras maculatus
Temp20–28°CpH5–6.5Size2.5 cmDietOmnivoreSwimMiddleDifficultyModerateDwarf rasbora
Boraras maculatus
- South America
Electric blue ram
Mikrogeophagus ramirezi var.
Temp26–30°CpH5–6Size4.2 cmDietOmnivoreSwimMiddleDifficultyModerateElectric blue ram
Mikrogeophagus ramirezi var.
- South America
Gold severum
Heros efasciatus var.
Temp22–29°CpH5–6.5Size20 cmDietOmnivoreSwimMiddleDifficultyModerateGold severum
Heros efasciatus var.
- Western Ghats of southern India (Goa, Karnataka, Kerala, Tamil Nadu)
Melon Barb
Haludaria fasciata
Temp22–26°CpH6–6.5Size6 cmDietOmnivoreSwimMiddleDifficultyModerateMelon Barb
Haludaria fasciata
- South America
Mendezs Dwarf Cichlid
Apistogramma mendezi
Temp23–29°CpH4–6Size6 cmDietCarnivoreSwimBottomDifficultyModerateMendezs Dwarf Cichlid
Apistogramma mendezi
- Asia
Neon Blue Rasbora
Sundadanio axelrodi
Temp23–26°CpH4–6.5Size2.5 cmDietOmnivoreSwimMiddleDifficultyHardNeon Blue Rasbora
Sundadanio axelrodi
- South America
Panda Uaru
Uaru fernandezyepezi
Temp27–30°CpH5–6.5Size19 cmDietOmnivoreSwimMiddleDifficultyModeratePanda Uaru
Uaru fernandezyepezi
- South America
Pictus cat
Pimelodus pictus
Temp22–25°CpH5.8–6.8Size12 cmDietOmnivoreSwimBottomDifficultyModeratePictus cat
Pimelodus pictus
- Asia
Snakehead Betta
Betta channoides
Temp23–30°CpH4–6.5Size4 cmDietCarnivoreSwimMiddleDifficultyModerateSnakehead Betta
Betta channoides
- South America
South American freshwater stingray
Potamotrygon motoro
Temp24–28°CpH5–6Size50 cmDietCarnivoreSwimBottomDifficultyHardSouth American freshwater stingray
Potamotrygon motoro
- South America
Threespot eartheater
Satanoperca daemon
Temp24–28°CpH3.5–6Size25 cmDietOmnivoreSwimBottomDifficultyModerateThreespot eartheater
Satanoperca daemon
- Asia
White Seam Betta
Betta albimarginata
Temp23–28°CpH4–6.5Size2.8 cmDietInsectivoreSwimMiddleDifficultyModerateWhite Seam Betta
Betta albimarginata