Pond: Koi Chemistry

Free to download. Every Pro feature is free for 48 hours, then a single one-time unlock — no subscription, no ads, no account. Works offline. Pond is the iOS koi pond chemistry assistant. Enter your test readings — pH, ammonia, nitrite, nitrate, KH, temperature — and get exact doses scaled to your pond volume. Brand-aware: pick the products on your shelf and Pond does the math. Features • Brand-aware dose math for Microbe-Lift, API Pondcare, Tetra Pond, and generics • Test & Adjust: 6-parameter readings → brand-cited recommendations + plain-English advisories • EPA free-ammonia equilibrium math (NH₃ from total ammonia, pH, temperature) • KH crash warnings before pH collapses overnight • Salt Bath calculator with 0.1% stress and 0.3% parasite targets • Plant-safety warnings — flags when salt protocols would kill water lilies, lotus, and submerged plants • Pond Volume estimator from length × width × average depth (rectangular or round) • Seasonal hints — spring ammonia spikes, summer DO drops, fall leaf load, winter dormancy • Locale-aware metric/imperial units (liters or gallons) • Named-source citations: Pond Informer, Microbe-Lift, EPA, Play It Koi, Central California Koi Society • Universal app for iPhone and iPad For koi keepers who want exact doses from the products they already have. Backyard ponds 500–3,000 gallons / 2,000–10,000 liters. No subscription, no ads, no account, no cloud. Free to download, with a one-time unlock for Pro. No subscription, no ads, no account, no cloud. Privacy: Pond collects nothing. No analytics, no accounts, no network requests. Your settings live on your device.