Swordtail: tank size, group & compatibility data

Stocking notes

Active livebearers that need more swimming length than their common shop size suggests.

For planning, StockingLab models Swordtail at its approximate adult size rather than the juvenile size commonly seen in shops. That matters because space use and waste production can change dramatically as fish mature.

What the calculator checks

• Whether the tank's usable volume is below the 100 L / 26.4 US gal reference minimum.
• Whether the selected group is below the planner's typical 4 fish social starting point.
• Whether target temperature and pH sit inside the planning range.
• Whether prospective tankmates create predation, fin-nipping, territorial or water-overlap conflicts.
• Whether too many fish accumulate in the same mid swim zone.

Before buying

Use this profile as a shortlist tool, not as a substitute for a dedicated care source. Confirm adult size, diet, sex ratio, habitat structure and locally relevant water conditions before purchase.

How to interpret this Swordtail profile

At roughly 10 cm / 3.9 in adult length, Swordtail should be planned at mature size rather than the smaller size commonly offered for sale. The reference tank is 100+ L / 26.4+ US gal, with a planning water window of 22–28°C and pH 7–8.3. A midpoint around 25.0°C and pH 7.7 is useful only as a comparison aid; the aim is stable water that overlaps the needs of the whole community.

The 4+ social starting point means tank size should be judged for the group, not for a single shop-sized fish. The modeled waste factor is 1.20×, so biological load is only one part of the decision; adult space, group size and swim-zone crowding still need to be checked. Activity is modeled at 1.15×, so the planner balances ordinary movement demand with adult size and mid-zone occupancy.

Common planning mistakes to avoid

• Treat the pH range of 7–8.3 as a compatibility window, not a target to force with rapid chemical changes.
• Prioritise tank length and open swimming room when comparing aquariums with similar volume.
• Check that the planned temperature sits inside the shared 22–28°C range for every species in the community.
• Use the 100 L / 26.4 US gal reference as a starting point, then let actual tank dimensions, filtration and the full stock list refine the decision.

Bottom line: the profile is designed to screen a proposed aquarium for obvious pressure points. A result that passes StockingLab still needs to be checked against current, species-specific husbandry information for Xiphophorus hellerii, especially diet, breeding behavior, sex ratio and habitat structure.