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. Free on the App Store.
Free on the App Store · iOS 17.0 or later · Version 1.0
SpawnOS is on the App Store
SpawnOS is free to download on the App Store for iPhone, and requires iOS 17.0 or later. It is built and published by Blackwater Aquatics Canada. There is no Android version and no paid download. Pro is an optional subscription bought on this website that removes the daily Ask SpawnOS limit.
Your SpawnOS account is the same one you use here, so records and any Pro subscription follow you onto every device you sign in on.
What a breeding project looks like
Every step below is included free.
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.
Free to download, free to use.
Register your animals, create pairs, record spawns and follow the whole timeline without paying. Pro removes the daily limit on Ask SpawnOS.