A fish built to leave through small holes
Scissortail rasboras earn their reputation honestly. They are slender, powerful swimmers that feed and travel in the upper half of the tank, move in fast bursts when startled or chasing, and — unusually — will jump repeatedly rather than once in a panic. Owners of uncovered or partly covered tanks lose them steadily, often through openings they dismissed as too small. With this species, assume any gap you can see is a door, and plan the top of the tank accordingly.
Seal, do not just cover
Fit a rigid lid across the whole surface, then treat the cut-outs as the real project: the spaces around filter inlets and outlets, heater cables and airline tubing are where scissortails exit. Fine mesh or snugly cut acrylic infill, checked for lifting corners, closes them. Mesh must be fine enough that a slim rasbora cannot push through a stretched square, and it should be secured, not laid loose — a determined fish jumping repeatedly can displace a draped piece.
Lower the water a few inches below the rim as a standing habit. For a fish that jumps from near the surface, that drop meaningfully lengthens the leap and brings the lid into play earlier. Recheck the whole seal after any equipment change or deep clean; a filter swapped at the weekend is a classic way a previously safe tank produces a floor fish the following week.
Reduce the bursts that become leaps
A settled school with open swimming length spends its speed horizontally. Scissortails kept in cramped conditions or too small a group are touchier, bunching and bursting at small disturbances. Plants at the ends and back break the tank into calmer zones without shortening the central run. Steady lighting changes and a predictable feeding approach lower the startle rate, and scattering food along the surface spreads the school instead of stacking it under one point where upward jostling turns into jumping.
Keep a cover, board or spare lid section over the open part of the tank throughout water changes; this species is quick enough to use the exact unguarded minutes, and fresh water tends to excite rather than sedate them.
When jumping increases, look for a cause
A rise in jumping from an established school is worth investigating rather than just tolerating behind a better lid. Test the water, confirm the filter flow has not failed or turned harsh, and review recent changes — new tankmates that chase, a moved light, increased traffic past the tank. Correct what has changed with matched, conditioned water changes and by removing a harassing tankmate if that is the pattern. A rasbora found out of water should be returned promptly with wet hands, kept in low light, and watched for surface damage; one that lies on its side or cannot rejoin the school needs prompt advice from an aquatic veterinarian or a trusted local fish service.
The seal on this tank is a set of specific spots, not a general impression, so KinsLe Family Sharing lets the rasboras' shared profile note exactly which cut-outs to press down and check, keeping every helper's closing routine identical.