Two traits to inspect
The official description names both sizes and mutations as things to discover. Treat them as separate fields: a size describes one characteristic, while a mutation identifies another variant.
The public description does not publish a size scale, mutation list, income multiplier table, or probabilities. This page does not assign numerical bonuses to either trait.
A useful variant record
- Exact species or fish name.
- Size label as displayed.
- Mutation label as displayed.
- Current income display.
- Observation date and any visible active boost.
Do not judge a variant only by color
Color or glow may help you notice something unusual, but live labels are better evidence for its identity. Promotional art is useful visual context; it is not a complete statistical description.
Before treating a hatch as a duplicate, check whether its traits differ from a fish you already own. If your goal is income, compare actual displayed earning rates as well.
Comparing variants fairly
Keep the species and other visible conditions as similar as possible. If several traits change at once, you cannot confidently attribute an income difference to one of them.
Keep an observation as an observation until it has enough context to support a general rule. One unusually valuable hatch does not establish a universal mutation multiplier.
Keep the fields separate
| Target | What to record | What it can establish |
|---|---|---|
| Fish name | Use the readable name supplied by the game. | A shared identity for comparing results; visual resemblance alone is weaker evidence. |
| Size | Copy the displayed size label or measurement, if present. | An observed size trait, without assuming an income or movement multiplier. |
| Mutation | Copy the displayed mutation label separately from size. | An observed variant; its name alone does not reveal a guaranteed bonus or chance. |
| Conditions | Keep the current earning value, visible boosts, and date. | Context for an income comparison and a reason to repeat it after changes. |
Read a comparison without overclaiming
Suppose two hypothetical fish have the same species label, one shows 10 income and the other 15, but both size and mutation differ. The second displayed value is 50 percent higher. That arithmetic does not identify which trait caused the difference, or establish a 1.5 times multiplier for either trait.
A stronger observation keeps the species, size, and other visible conditions fixed while comparing a mutation, or keeps the mutation fixed while comparing size. When you cannot isolate a trait, describe the whole result instead. A dated record still helps a collector decide what to keep without inventing a statistical rule.
Questions about this step
Is a glowing or differently colored fish always mutated?
Use the live label to identify the trait. Appearance can prompt a closer look, but an effect or promotional image is not a complete mutation record.
How should I report a possible new variant?
Keep the exact fish, size, and mutation labels, the date, and a readable screenshot with context. Include the current earning display if the claim concerns income.
Sources and scope
- Steal Fish Eggs: official Roblox experience
Checked October 1, 2026. The developer's description supports egg stealing, hatching fish, fish income, endless-pool training, pool/base upgrades, player theft, sizes, and mutations.
- Roblox game metadata: universe 10718240577
Checked October 1, 2026. Confirms place 99183404085821, creator fishy fish fish!, and the September 26 update timestamp. Metadata does not provide a species roster or a gameplay formula.
Planning methods and worked examples are the wiki's editorial guidance. Example numbers are hypothetical. We have not performed a live-account gameplay test; exact prices, hatch odds, timers, and multipliers require current game evidence.
How we review sources and corrections