🧭 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.

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🧪 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.

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🎯 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).

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🛠️ How to Use Tap Water Safely (Step-by-Step)

1. 🧪 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.
2. 🧴 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.
3. 🌡️ Match temperature
   • Keep within ±1–2°F (±0.5–1°C) of tank water to avoid thermal stress.
4. 💨 Maximize oxygen during/after fills
   • Aim returns to ripple the surface; add an airstone if fish breathe faster post-change.
5. 🧯 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.
6. 🧰 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.
7. 🦐 For shrimp/snails
   • Copper must be ~0. If present, use carbon/chemi-absorbers or switch to RO/DI + shrimp salts.
8. 🧂 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.

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🧊 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.

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🚩 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.

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🧰 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).

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🧑‍🔬 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.

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📋 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