Free tools
Freshwater keeper tools
Calm, honest little helpers for the questions that keep keepers up at night — starting with the water. Free, no sign-up, nothing saved.
Stocking & tank-size calculator
The number one beginner mistake is too many fish in too little water. Tell us your tank and your wish-list — we'll check each fish against its fact-checked minimum tank and group size, flag clashes, and estimate how full the tank is.
Cycle Coach
The nitrogen cycle is the step nobody explained. Log your ammonia, nitrite and nitrate and we'll tell you which stage you're in, what to do next, when to test again, and when it's finally safe to add fish. Set a test reminder so you never lose track. Saves in your browser.
Aquarium care scheduler
Once the tank's running, the job becomes a rhythm — feeding, testing, water changes and filter care. Pick your tank type for a daily / weekly / monthly routine you can print, or add the reminders straight to your calendar so a water change never slips.
Water-parameter interpreter
You tested the water — now what do the numbers mean? Enter your ammonia, nitrite, nitrate and pH and get a plain-English read on whether your fish are fine or your water needs work.
Setup safety audit
Is your tank about to cause trouble? Pick your fish and tick what you've done — you'll get a plain-English risk report: the setup gaps to close, the numbers to confirm, and the warning signs that mean test your water and get advice.
Is my fish okay? Symptom checker
Something looks off? Tick what you're seeing on a sick fish, shrimp or snail and get possible causes and safe first steps — always leading with the water. Honest triage, never a diagnosis or a drug dose.
Tankmate compatibility checker
Will these fish get along? Tick any combination and we check every pair for temperature clashes, predators vs shrimp, the betta solo rule and water-hardness mismatches — before you buy, not after.
Which fish is right for me?
Not sure where to start? Tell us your tank size, whether it's heated, and your water hardness — and get matched to beginner-friendly fish that actually fit, each with a fact-checked guide.
Compare two fish
Torn between two fish? Pick any two and see them side by side — difficulty, tank size, water parameters, temperament, diet and lifespan — straight from our fact-checked care sheets, so it can never contradict the full guide.
All free, no sign-up, nothing saved. More species and tools as Finfern grows.