The difference between a hobbyist who breeds fish and a breeder who improves fish is record-keeping. Every serious guppy, betta, or shrimp breeder I know keeps detailed logs of their crosses, spawn dates, fry counts, mortality rates, and trait expression. The ones who do not keep records eventually lose track of which line produced which results, repeat failed crosses, and cannot explain why their fish quality plateaued.
You do not need expensive software. A notebook works. A spreadsheet works. An app works. What matters is that you record consistently and review your data periodically. This guide covers the best options across all formats.
What to Track in a Breeding Log
Before choosing a format, know what information actually matters:
Essential Data (Track Every Spawn)
- Date of spawn/birth
- Parent identification (tank number, strain name, color description, or unique markings)
- Number of fry (or eggs for egg-layers)
- Fry survival count at 1 week, 2 weeks, and 4 weeks
- Water parameters at time of spawn (temp, pH, GH minimum)
- Any unusual observations (deformities, color anomalies, behavioral notes)
Advanced Data (For Selective Breeding)
- Parent lineage (who were the grandparents?)
- Trait grading of offspring at 6-8 weeks (color intensity, fin shape, body form)
- Cull/keep ratio — what percentage of fry met your quality threshold?
- Cross type — inbred (same line), outcross (different line), hybrid (different strain)
- Generation number — F1, F2, F3, etc. from the founding pair
Option 1: Printable Spreadsheet Templates
The simplest and most accessible option. Create a spreadsheet with columns for each data point listed above, print it, and keep it near your fish room. Fill in entries by hand after each spawn.
Basic Template Structure
| Date | Tank | Male ID | Female ID | Fry Count | Survival (1wk) | Survival (4wk) | Notes |
|---|---|---|---|---|---|---|---|
| 4/16/2026 | T3 | Moscow Blue M1 | Moscow Blue F2 | 28 | 24 | 21 | Strong color in males at 6wk |
| 4/22/2026 | T5 | Platinum M3 | Platinum F1 | 35 | 30 | 26 | 3 bent spines culled |
Pros: No technology required. Tangible and always accessible. Easy to customize. Cons: Not searchable. Gets messy over time. Paper can be lost or damaged.
Where to Get Templates
- Google Sheets — create your own with the columns above, or search “fish breeding log template” for community-shared templates
- Excel — same approach, offline storage
- Notion — database-style templates with relational linking between parent records and offspring records
Option 2: Dedicated Aquarium Apps
Several mobile apps are designed for aquarium management and include breeding log features:
Aquarimate
A comprehensive aquarium management app that includes tank parameter logging, fish inventory, and breeding records. The breeding log feature lets you tag parent fish, record spawn events, and track fry batches over time.
Best for: Breeders who want breeding logs integrated with their overall tank management (water change schedules, parameter tracking, equipment maintenance).
AquaNote
Focused on logging and tracking rather than full tank management. Simple interface for recording water parameters, fish additions/removals, and breeding events. The timeline view makes it easy to see patterns across multiple spawns.
Best for: Breeders who want a quick, low-friction way to log events without navigating complex menus.
MyAquarium
Another full-featured aquarium app with species database, parameter tracking, and breeding log capabilities. The species database is helpful for looking up breeding conditions and compatibility.
Best for: Beginners who want species care information alongside their breeding records.
Option 3: Custom Database (Google Sheets or Airtable)
For serious breeders managing multiple lines, a relational database is the most powerful option. Airtable and Google Sheets with linked tables let you create a system where:
- Each fish has a unique record with lineage information
- Spawn events link to both parents and resulting offspring
- Offspring records link back to their spawn event
- You can filter and sort by any field — show all spawns from a specific male, all F3 generation fish, all spawns with above-average fry survival
Sample Database Structure
Table 1: Fish Registry
| Fish ID | Strain | Sex | Source | Gen | Status | Tank |
|---|---|---|---|---|---|---|
| MB-M01 | Moscow Blue | M | Aquabid | F0 | Active | T3 |
| MB-F02 | Moscow Blue | F | Aquabid | F0 | Active | T3 |
| MB-M12 | Moscow Blue | M | Self-bred | F1 | Active | T5 |
Table 2: Spawn Log
| Spawn ID | Date | Male | Female | Fry Count | Survival 4wk | Quality Notes |
|---|---|---|---|---|---|---|
| S-001 | 4/16/2026 | MB-M01 | MB-F02 | 28 | 21 | 4 strong hikari, 6 moderate |
Table 3: Offspring Grading
| Fish ID | Spawn ID | Grade | Trait Score | Disposition |
|---|---|---|---|---|
| MB-M12 | S-001 | A | 8.5/10 | Keep (breeder) |
| MB-F13 | S-001 | B | 6/10 | Rehome |
This level of record-keeping is overkill for casual breeders but essential for anyone working on multi-generation selective breeding projects. When you are five generations deep into a Moscow Blue line and need to decide which F5 male to pair with which F4 female, having complete lineage data makes the difference between guessing and making informed decisions.
Option 4: The Notebook Method
A dedicated notebook — physical, analog, paper — is how many of the best breeders in the world keep their records. Japanese medaka breeders, German guppy breeders, and Thai betta breeders have been using notebooks for decades, and their fish quality speaks for itself.
How to set it up:
- One page per breeding tank or breeding pair
- Date each entry
- Record spawns, fry counts, observations, and water parameters
- Tape or glue photos of standout fish to the page
- Use tabs or dividers to separate different strains or lines
The advantage of notebooks: They force you to write by hand, which improves memory retention. You remember your breeding results better when you physically write them than when you type them into an app. For a hobby that rewards pattern recognition and intuition built over many generations, this matters.
What Your Records Should Tell You After One Year
If you have been keeping good records for 12 months, you should be able to answer these questions:
- Which breeding pair produces the highest quality offspring? (Trait scores and grading data)
- What is your average fry survival rate? (Survival counts across all spawns)
- Is your line improving generation over generation? (Compare trait scores across F1, F2, F3)
- What water parameters correlate with the best spawns? (Parameter data at time of spawn)
- How much inbreeding depression are you seeing? (Deformity rates, fry size, fertility data)
- When do your fish spawn most actively? (Date patterns — seasonal, lunar, temperature-based)
If your records cannot answer these questions, you are not recording enough detail. If they can, you have the data foundation to make breeding decisions that improve your fish over time rather than just maintaining the status quo.
Start Simple, Add Complexity Later
The biggest mistake with breeding logs is overengineering them on day one. You design a complex database with 30 fields per record, fill it out diligently for two weeks, then abandon it because it takes longer to log a spawn than to raise the fry.
Start with the bare minimum: date, parents, fry count, and one sentence of notes. Do this for every spawn for three months. Once the habit is established, add fields as you realize what information you actually need. A simple log that you maintain consistently beats a complex system that you abandon after a month.
The best breeding log is the one you actually use.