Best Aquarium Fish for Blackwater Tanks

A blackwater aquarium is one of the most striking setups in the freshwater hobby. Dark amber water, tannin-stained driftwood, leaf litter, and dim lighting recreate the peat swamps and jungle rivers of Southeast Asia and South America. The fish that thrive in this environment are some of the most exotic and beautiful in the hobby.

What Is a Blackwater Aquarium?

Blackwater refers to water with naturally low mineral content, low pH (4.5–6.5), and high tannin content from decomposing organic matter. You recreate this in an aquarium using:

• Botanicals (catappa leaves, seed pods, driftwood bark)
• Dark or natural substrate
• Minimal hardscape decoration
• Dim or warm-toned lighting

Best Fish for Blackwater Tanks

1. Discus

Discus are the crown jewel of blackwater fishkeeping. These large, laterally compressed cichlids from the Amazon require soft, acidic water (pH 5.5–6.5), warm temperatures (28–31°C), and pristine water quality. Their colours — red, blue, pigeon blood, and spotted — intensify dramatically in blackwater conditions.

Tank: 150+ litres | Temp: 28–31°C | pH: 5.5–6.5

2. Cardinal Tetra

Cardinal tetras are the natural schooling companion of discus in the wild. Their neon red and blue colouration is at its most vivid in soft, acidic blackwater. Keep schools of 15 or more.

Tank: 60+ litres | Temp: 23–28°C | pH: 5.5–7.0

3. Chocolate Gourami

The chocolate gourami is a delicate, stunning fish from the blackwater streams of Southeast Asia. Its brown body and cream banding look extraordinary against tannin-stained water. It requires very soft, acidic water to thrive.

Tank: 60+ litres | Temp: 25–30°C | pH: 4.5–6.5

4. Licorice Gourami

Licorice gouramis are tiny labyrinth fish from the peat swamps of Sumatra and Borneo. Males display vivid blue iridescence during courtship. They are best kept as a species-only group or with very small, peaceful companions.

Tank: 30+ litres | Temp: 24–28°C | pH: 4.0–6.5

5. Pencilfish (Nannostomus species)

Pencilfish are slender, elegant tetras that hover diagonally in the water column. Their red and gold striped bodies look exquisite in amber blackwater. They are slow feeders and do best away from boisterous species.

Tank: 40+ litres | Temp: 23–28°C | pH: 5.0–7.0

6. Apistogramma (Dwarf Cichlids)

Apistogrammas are small South American cichlids that thrive in soft, acidic conditions. Males display extraordinary yellows, blues, and reds. They do well as a pair or harem in a planted blackwater tank.

Tank: 60+ litres | Temp: 24–28°C | pH: 5.0–7.0

7. Betta (Wild Types)

Wild-type bettas — including Betta imbellis and Betta albimarginata — thrive in the blackwater peat swamps of their native range. They are far calmer than commercial bettas and can sometimes be kept in pairs or species groups.

Tank: 40+ litres | Temp: 24–28°C | pH: 4.5–6.5

Setting Up Your Blackwater Tank

1. Use RO or soft tap water (GH < 6°)
2. Add catappa leaves and seed pod botanicals
3. Allow tannins to tint the water naturally — water should be amber, not black
4. Use a dark substrate (black sand or fine dark gravel)
5. Keep lighting dim — floating plants reduce surface light naturally

Shop our blackwater botanicals and specialty livestock to build your blackwater setup today.