Can Arapaima and Mystery Snail Live Together?

Arapaima is a semi-aggressive species (7/10), while Mystery Snail is peaceful (0/10). This notable difference means Arapaima may occasionally assert dominance over Mystery Snail.

Large aggression gap (7 points) between Arapaima and Mystery Snail increases stress risk for the more peaceful fish.

Arapaima and Mystery Snail both frequent the Top (Surface) and Middle (Open Water) region of the setup. This overlap can increase competition for space, so providing ample room and cover is important to keep both species comfortable.

Worth noting: Arapaima is a known jumper, so a tight-fitting lid is essential.

To improve the chances of a peaceful coexistence in this community tank: A larger aquarium with ample hiding spots can help diffuse aggression and give the less dominant fish space to retreat.

The safe temperature window for both species falls between 24°C and 28°C. Aim for the midpoint of this range (around 26.0°C) for optimal comfort.

Both fish can tolerate a pH between 7 and 7.5. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 8–15 dGH. Regular testing will ensure conditions stay within this range.

To house Arapaima and Mystery Snail together, plan for an aquarium of at least 15000 litres with a minimum length of 600 cm. This recommendation combines the stricter species minimums with a community-load allowance so the pairing has realistic long-term space and filtration headroom.

Because this pairing requires extra vigilance, include plenty of hiding spots — caves, driftwood, and dense plant clusters — so the less dominant fish can retreat when needed.

Specific environmental needs for this combination include: Established Algae (Otocinclus). Meeting these requirements will help both species thrive.

Both species do well with low (still water) water movement, so a standard filtration setup rated for the tank volume should suffice.