Stop tracking spawns
in your camera roll.
SpawnOS keeps your breeding pairs, spawn dates, fry milestones and lineage in one place — and tells you what should be happening in the tank today. Your first breeding project is free.
Where the app is right now
SpawnOS for iPhone is in TestFlight with invited testers while we finish the App Store release. It is a real, working build — the breeding engine, timelines, lineage and assistant all run against the same account you would use here. If you have an invitation, open it on your iPhone to install.
Not a tester yet? Create a free SpawnOS account below — it is the same login the app uses, so you will be ready the day the App Store listing opens.
What a breeding project looks like
Every step below is included free for your first project.
Register your fish
Name them, record species, sex, traits and photos. This is the stock list you already keep in your head.
Build the pair
Pick two parents. SpawnOS checks species and sex, shows what to expect from their visible traits, and warns you if they are related.
Record the spawn
One date is all it takes. SpawnOS builds the timeline from there — hatch, free-swimming, first feeding, when to pull the male.
Follow the milestones
Each stage shows its expected window and what to watch for. Confirm what actually happened and the rest of the timeline adapts.
Keep the lineage
Register offspring against the spawn and SpawnOS links the generations for you, so relatedness warnings get smarter as your lines grow.
What SpawnOS does and doesn’t know
Breeding biology varies enormously between species, and an app that pretends otherwise will give you confidently wrong dates. SpawnOS is built to say what it actually knows.
- Verified timelines: Betta splendens and guppies have SpawnOS-reviewed milestone windows.
- Everything else: mollies, platies, Neocaridina shrimp, corydoras, angelfish and clownfish register and track today. Where SpawnOS has researched a species profile it labels how confident it is — and where it has none, it says the timeline isn’t available rather than borrowing another species’ biology.
- Trait predictions, not genotypes: SpawnOS reads the visible traits you record on both parents and tells you what tends to show up in the fry. It does not know your fish’s genotype, and it does not claim to. Marble and koi patterning in particular are called out as unstable rather than predicted.
Your first breeding project is free.
Register your animals, create a pair, record the spawn and follow the whole timeline without paying. Pro is for the point where you want to run a second line alongside the first.