🧭 Quick Decision Guide
- ✅ Use tap (freshwater community/most cichlids/planted):
Treat with a conditioner that handles chlorine and chloramine and test GH/KH/pH.
- ⚠️ Tap is OK with extra care (shrimp, softwater specialists, brackish):
Consider mixing tap + RO/DI or remineralizing to exact targets; test copper for shrimp.
- 🚫 Avoid tap (reef/marine, high-end corals, problem tap):
Use RO/DI (0–10 TDS) to prevent algae-fueling phosphate/silicate and metals.
🧪 What to Test First (tap source)
- 🧪 Chlorine/Chloramine (must be neutralized)
- 🧪 pH / KH / GH (stability + hardness)
- 🧪 Nitrate (NO₃⁻) and Phosphate (PO₄³⁻)
- 🧪 Copper (Cu) if you keep shrimp/snails/inverts
- 🧪 TDS (helpful snapshot; not a target by itself)
🧠 Letting water “sit out” removes some chlorine but not chloramine. Always use a chloramine-capable conditioner.
🎯 Target Ranges (use as a starting point)
- 🟢 Freshwater community (tetras, barbs, gourami):
pH 6.5–7.8 • KH 3–8 dKH • GH 4–12 dGH • NO₃⁻ <20–30 ppm
- 🌿 Planted: same as above; CO₂ users like KH 3–6 dKH for pH stability.
- 🟡 Livebearers/African rift cichlids (hard/alkaline):
pH 7.6–8.6 • KH 6–12 dKH • GH 10–20 dGH
- 🦐 Neocaridina shrimp: pH 6.8–7.6 • KH 2–6 • GH 6–10 • Cu ≈ 0
Caridina often need softer, lower KH (many use RO + shrimp salts).
- 🟤 Brackish: SG 1.005–1.015 (hydrometer/refractometer) • Match KH higher.
- 🔵 Marine/reef: RO/DI + salt mix • SG 1.025 ±0.001 • Alk stable • NO₃⁻ 2–20, PO₄ 0.03–0.10 (reef).
🛠️ How to Use Tap Water Safely (Step-by-Step)
- 🧪 Profile your tap
- Run water 2–3 min, collect, aerate 30–60 min, then test pH/KH/GH (CO₂ degassing can raise pH—measure after aeration).
- Check chlorine/chloramine, NO₃/PO₄, and copper if keeping inverts.
- 🧴 Condition it correctly
- Use a conditioner that neutralizes chlorine & chloramine and temporarily binds ammonia (released when chloramine is broken).
- Dose for the entire volume you’re adding. For large changes, you can:
- 🪣 Treat in a pre-mix bin, or
- 🚿 Dose the tank for the full incoming volume, then refill.
- 🌡️ Match temperature
- Keep within ±1–2°F (±0.5–1°C) of tank water to avoid thermal stress.
- 💨 Maximize oxygen during/after fills
- Aim returns to ripple the surface; add an airstone if fish breathe faster post-change.
- 🧯 If you have chloramine:
- Expect a temporary total-ammonia reading after conditioning (it’s bound).
- Keep biofilter healthy; if you’re cycling, don’t overfeed that day.
- 🧰 For planted tanks
- Tap often supplies helpful KH/GH. If KH is very low (<2 dKH), add buffer to avoid pH swings (especially with CO₂).
- If GH is very high and you grow soft-water plants, blend with RO/DI.
- 🦐 For shrimp/snails
- Copper must be ~0. If present, use carbon/chemi-absorbers or switch to RO/DI + shrimp salts.
- 🧂 Household water softeners (ion-exchange)
- Avoid as a sole source: they swap Ca/Mg for sodium, yielding odd GH/KH balance. Use bypass or mix with RO/DI, then remineralize.
🧊 Top-Offs vs. Water Changes
- 💧 Top-off replaces evaporated water only (no minerals leave when water evaporates).
- Freshwater: top off with dechlorinated tap; note minerals accumulate over time → regular water changes reset.
- Marine: RO/DI only for top-off (salt stays behind).
- 🔁 Water changes export nitrates, DOC, and excess minerals—still essential even with clean tap.
🚩 When Tap Water is a Bad Idea
- 🧪 Nitrate > 20–30 ppm or phosphate high straight from the tap (algae issues).
- 🧲 Copper detectable (old copper plumbing) and you keep inverts.
- 🏭 Noticeable chemical odors, discoloration, or well water with iron/sulfur you can’t filter reliably.
👉 Switch to RO/DI (or blend with tap), then remineralize to your targets.
🧰 Practical Setups That Work
- 🛢️ Pre-mix bin (32–44 gal food-safe can): dechlorinate, heat, aerate, and pump to tank for big/sensitive water changes.
- 🧴 Inline carbon block on a fill hose can reduce chlorine/chloramine load (still use conditioner).
- 🧪 Keep liquid test kits (not just strips) for NH₃/NH₄⁺, NO₂⁻, NO₃⁻, pH (+ GH/KH kit, copper if inverts).
🧑🔬 Examples
- Your tap: pH 7.6, KH 6, GH 8, 0 chlorine (after treatment), NO₃ 5 →
✅ Great for community/planted with conditioner.
- Your tap: pH 8.2, KH 10, GH 18, NO₃ 15 →
✅ Great for livebearers/African cichlids; for soft-water tetras, mix 50/50 with RO/DI.
- Your tap: Cu detectable, NO₃ 40 →
🚫 Use RO/DI; remineralize for shrimp/fish; use tap only after fixing plumbing/filtration.
📋 Quick Checklist (print me)
- 🧪 Test: Chlorine/Chloramine, pH, KH, GH, NO₃, PO₄, Copper (if inverts)
- 🧴 Conditioner: neutralizes chlorine & chloramine; binds ammonia
- 🌡️ Temp-match within ±1–2°F (±0.5–1°C)
- 💨 Strong surface agitation during/after refill
- 🧂 Avoid softened water as sole source; mix RO/DI if needed
- 🔁 Keep doing regular water changes; top-off ≠ water change
