Can Harlequin Shark and Malaysian Trumpet Snail (MTS) Live Together?

Harlequin Shark is a semi-aggressive species (8/10), while Malaysian Trumpet Snail (MTS) is peaceful (0/10). This notable difference means Harlequin Shark may occasionally assert dominance over Malaysian Trumpet Snail (MTS).

Large aggression gap (8 points) between Harlequin Shark and Malaysian Trumpet Snail (MTS) increases stress risk for the more peaceful fish.

Harlequin Shark and Malaysian Trumpet Snail (MTS) both frequent the Bottom (Substrate) 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: Malaysian Trumpet Snail (MTS) is nocturnal and will be most active after lights-out, naturally reducing daytime encounters.

To improve the chances of a peaceful coexistence in this community tank: Provide a significantly larger tank (at least 50% more volume than the minimum) to allow both Harlequin Shark and Malaysian Trumpet Snail (MTS) to establish separate territories. Add plenty of line-of-sight breaks using driftwood, rocks, and dense planting to reduce territorial confrontations. 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 21°C and 27°C. Aim for the midpoint of this range (around 24.0°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 Harlequin Shark and Malaysian Trumpet Snail (MTS) together, plan for an aquarium of at least 150 litres with a minimum length of 120 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: Sand (Sifters), Driftwood (Digestion/Hiding), Established Algae (Otocinclus), Soil / Nutrient Rich. Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Harlequin Shark requires Sand (Sifters), while Malaysian Trumpet Snail (MTS) requires Soil / Nutrient Rich. These substrate types may be difficult to provide simultaneously. Compromise where possible or prioritise the more critical need.

Harlequin Shark prefers High (River/Stream) flow while Malaysian Trumpet Snail (MTS) needs Low (Still Water) flow. Consider positioning filter outlets and using baffles to create zones of different current intensity within the same tank.

This pairing usually fails when the tank is treated like a standard mixed community and the caution flags are ignored. Harlequin Shark and Malaysian Trumpet Snail (MTS) need extra room, more cover, and closer observation during the first few weeks so small aggression, feeding, or territory issues do not snowball into a long-term problem.