Leopard Gecko Het Genetics: What 'Het For' Means
| Het x het (same gene) visual odds | ~25% per egg |
| Het x het carrier odds | ~50% per egg |
Why hets look normal
Recessive morph traits only show visually when a gecko has two copies of the gene — one from each parent. A gecko with just one copy is a 'het' carrier: genetically carrying the trait but visually indistinguishable from a normal, non-carrier gecko.
The basic het x het math
Pairing two geckos that are both het for the same recessive gene follows standard Mendelian expectations: roughly a 25% chance per egg of a visually morphed hatchling, roughly 50% chance of a het (carrier, normal-looking) hatchling, and roughly 25% chance of a non-carrier, normal-looking hatchling.
These are probabilities, not guarantees
These percentages describe the statistical odds across many eggs, not a guarantee for any single clutch — a small clutch can easily land outside the expected ratio purely by chance, the same way a coin flip doesn't guarantee exactly 50/50 over just a few flips.
Why 'possible het' shows up in listings
A gecko can be listed as 'possible het' when it's produced from a pairing that statistically could have passed on a recessive gene, but without a visual or genetically confirmed offspring test, the exact het status can't be stated with certainty.
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A single adult leopard gecko needs a 20-gallon long tank as an absolute minimum, with a 36x18 in (40-gallon breeder) footprint now considered the recommended standard — plus a secure lid, an under-tank heater on a thermostat, a thermal gradient, at least three hides, and a shallow water dish.
Set up in this order: substrate, then heat source wired through a thermostat, then hides and water dish, then decor — and run the whole enclosure for at least 24–48 hours to confirm stable temperatures before your gecko moves in.
Hatchlings can start in a 10-gallon tank or tub, juveniles do well in 20 gallons, and adults need a 20-gallon long as an absolute minimum — with 36x18 in (40-gallon breeder) now the widely recommended standard, not just an upgrade.
Heat a leopard gecko enclosure with an under-tank heater and/or overhead heat source (halogen or deep heat projector) wired through a thermostat — a thermostat is mandatory, not optional, and heat rocks should never be used.
Leopard geckos can survive without UVB using dietary D3 supplementation, but current husbandry guidance now recommends low-level UVB (roughly 2–6% T5) as best practice — it improves D3 synthesis, bone density, and natural behavior, and views on it have shifted significantly from older nocturnal-species advice.
Keep ambient humidity around 30–40% across most of the enclosure, with a dedicated humid hide raised to roughly 70–80% to support smooth, complete sheds.