Bringing home a new fish or coral is exciting—but it’s also the moment many reef tanks get hit with stress, disease, or pests. The good news: a calm, repeatable process dramatically improves survival and reduces problems like ich, coral flatworms, and sudden parameter shock.
This guide is built for beginners and focuses on best practices to introduce new fish to a saltwater aquarium and add coral to a reef tank safely.
Why introductions go wrong (and how to prevent it)
Stress + parameter mismatch
Most losses happen from rapid changes in:
- Temperature (°F/°C)
- Salinity (ppt or specific gravity)
- pH (especially after shipping)
- Ammonia exposure in shipping water
Safety note: Avoid “chasing numbers” during acclimation. Your goal is matching temperature and salinity, then providing stable, clean water—not making perfect test-kit readings in a bucket.
Disease risks (ich, velvet, brooklynella)
Many fish arrive carrying parasites even if they look fine. Common ones include:
- Marine ich (Cryptocaryon irritans)
- Velvet (Amyloodinium) — often faster and more lethal than ich
- Brooklynella — common in clownfish
If you’re wondering how to prevent ich in a reef tank, the most reliable answer is: don’t introduce it in the first place through proper quarantine and observation.
Pest risks on corals (aiptasia, flatworms, nudis)
Corals can carry hitchhikers that multiply in your display:
- Aiptasia
- Flatworms
- Nudibranchs (especially on zoas and montis)
- Red bugs (Acropora)
- Vermetid snails, bryopsis, bubble algae
A good coral dipping guide helps reduce risk, but dips are not a cure-all—eggs often survive dips.
Before you buy: readiness checklist (beginner-friendly)
Tank maturity and stability (temperature, salinity, nutrients)
Before adding anything, aim for stable, repeatable numbers:
Beginner-friendly targets (typical reef ranges):
- Temperature: 77–79°F (25–26°C), stable within ~1°F/day
- Salinity: 35 ppt (SG ~1.026), stable
- Ammonia (NH3/NH4+): 0 mg/L
- Nitrite (NO2-): 0 mg/L
- Nitrate (NO3-): often 5–20 mg/L is workable for mixed reefs
- Phosphate (PO4): often 0.03–0.10 mg/L is workable for mixed reefs
- Alkalinity: commonly 7–9 dKH, prioritize stability
Safety note: If your tank is new or recently changed (new sand, big rock move, filter change), slow down and confirm ammonia stays at 0 mg/L for a few days.
Compatibility basics (fish temperament, coral needs)
Quick beginner checks:
- Fish: research adult size, diet, and temperament (bullies can make new fish hide and stop eating).
- Corals: match to your system’s lighting/flow and your comfort level:
- Soft corals: generally forgiving
- LPS: moderate care, watch sweeper tentacles
- SPS: more demanding; stability matters most
Equipment you should have on hand
- Heater + thermometer (for QT and acclimation container)
- Refractometer (or calibrated digital salinity meter)
- Buckets/containers dedicated to aquarium use
- Airline tubing + valve/clip for reef tank acclimation (drip acclimation)
- Test kits: ammonia, nitrate, phosphate (and alkalinity if keeping stony corals)
- Coral dip + coral tools (tongs, turkey baster)
- Coral mounting supplies: cyanoacrylate gel, epoxy putty
- Quarantine setup (recommended): small tank, filter, heater, lid, hiding places
Best practice for adding a new fish (step-by-step)
Quarantine first (the safest path)
If you can only adopt one habit that improves success, choose this: quarantine saltwater fish.
Goals of quarantine (QT):
- Observe for disease (spots, flashing, rapid breathing, frayed fins)
- Ensure the fish is eating well
- Treat if needed (in QT—not in your reef display)
How long to quarantine fish?
- Common beginner-friendly recommendation: 2–4 weeks observation in QT.
- Longer is sometimes used, but the key is consistency and careful observation.
Daily QT checklist:
- Confirm temperature and salinity match your display
- Check for heavy breathing, scratching, clamped fins
- Offer appropriate foods (start easy: frozen mysis, enriched brine, pellets)
- Test ammonia frequently in QT (small tanks swing fast)
Safety note: Many medications are not reef-safe. Treating parasites typically requires QT. Do not dose parasite meds into a display with corals/inverts unless you are 100% sure it’s compatible (most aren’t).
Acclimation day
This is where acclimation temperature salinity match matters most.
1) Temperature equalization
- Float the sealed bag for 10–20 minutes (or place the fish container near the sump/QT heater).
- Keep lights low.
2) Salinity match and drip acclimation basics
- Measure the bag water salinity with a refractometer (quick sample).
- If salinity differs notably from your QT/display, use drip acclimation:
- Place fish + bag water in a clean container.
- Start a siphon with airline tubing, 2–4 drips/second.
- Aim for 30–60 minutes total in most cases (longer isn’t always better if shipping water is poor).
3) Avoiding contaminated bag water in the display
- Net the fish or use a specimen container.
- Do not pour bag water into your display tank.
Safety note: If a fish was shipped and the bag water smells strongly or looks cloudy, avoid extended acclimation in that water. Prioritize getting the fish into clean, temperature-matched water with stable salinity.
Minimizing aggression
New fish aggression (reef tank compatibility) is real—especially with tangs, damsels, dottybacks, and established clowns.
Beginner-friendly tools:
- Acclimation box (best): let the new fish be seen but not chased for 1–3 days.
- Feed small amounts before release (reduces territorial behavior).
- Consider minor rockwork adjustments only if safe and your tank is stable (avoid sand storms and coral damage).
- Dim or shorten lights on introduction day.
The first 72 hours
What you want to see:
- Exploring, brief hiding, then returning to swim/peck
- Eating within 24 hours (some take longer, but appetite should improve)
- Normal breathing (not frantic)
Red flags:
- Rapid breathing at the surface or by a powerhead
- Lying on the bottom, repeated crashing into rocks
- White “dust” look, heavy mucus, or sudden lethargy
- Not eating after 48–72 hours (depends on species)
Test ammonia (especially in newer systems):
- Display and QT should remain 0 mg/L ammonia and 0 mg/L nitrite.
Best practice for adding a new coral (step-by-step)
Inspect before it enters your tank
Before any dip, do a careful look under white light:
- Check the base and underside for eggs or hitchhikers
- Look for algae tufts, aiptasia, vermetids
- Inspect tissue: tears, exposed skeleton, brown jelly (LPS warning sign)
Tip: Use a turkey baster to gently blow the coral—pests often release or move.
Dip and rinse (pest management)
A coral dip helps reduce coral pests (flatworms, nudibranchs, red bugs), but remember:
- Dips often don’t kill eggs
- Dips reduce risk; they don’t guarantee pest-free corals
Simple dip workflow (beginner-friendly):
- Prepare a dip container with tank water.
- Add dip per the product directions (follow label precisely).
- Dip for the recommended time (often 5–15 minutes, product-dependent).
- Move coral to a separate rinse container of clean tank water.
- (Optional) Second rinse container for extra safety.
- Then place coral in the tank.
Safety note: Never mix dip chemicals with display water. Always use dedicated containers and discard dip/rinse water afterward.
Light and flow acclimation
Most new-coral losses are light shock, not “bad coral.” If you’re asking how to acclimate corals to new lighting without bleaching them, start lower than you think.
Beginner method:
- Start the coral lower in the tank and in moderate flow.
- Reduce light intensity or photoperiod for a few days if possible.
- Ramp up slowly over 1–3 weeks (slower for SPS).
Placement basics (quick guide):
- Soft corals (zoas, leathers, mushrooms): low–moderate light, low–moderate flow
- LPS (hammer, torch, frogspawn, acans): moderate light, moderate flow (avoid blasting flesh)
- SPS (Acropora, Montipora): higher light, strong turbulent flow, very stable alkalinity
Mounting and stability
- Use cyanoacrylate gel for frags; epoxy can help secure larger bases.
- Dry the frag plug/rock briefly with a paper towel for better bond.
- Avoid getting glue on living tissue (especially LPS flesh).
- Ensure the coral can’t tip over (falls cause tissue damage).
Post-add monitoring
In the first week, watch:
- Polyp extension (good sign, not the only sign)
- Tissue recession, bleaching, or brown jelly (urgent for LPS)
- Unusual closed behavior in zoas (check for nudis/eggs)
Stony coral note:
- Adding LPS/SPS increases demand for carbonate. Monitor alkalinity (dKH) and keep it stable. Sudden shifts (even “toward perfect”) can cause issues.
Water parameters that matter most during introductions
Fish-focused priorities
- Temperature: 77–79°F (25–26°C), stable
- Salinity: 35 ppt (SG ~1.026), stable
- Ammonia: 0 mg/L
- Nitrite: 0 mg/L
- Nitrate: keep reasonable and stable (avoid big swings)
Coral-focused priorities
- Alkalinity: commonly 7–9 dKH, keep changes small (avoid > ~0.5–1.0 dKH/day)
- Calcium: often 400–450 mg/L
- Magnesium: often 1250–1400 mg/L
- Nutrients: avoid sudden “too clean” changes
- Nitrate: commonly 5–20 mg/L
- Phosphate: commonly 0.03–0.10 mg/L
Safety note: Stability beats perfection. Don’t make large corrections the same day you add a new coral.
How Reef Buddy can help (light mention)
Reef Buddy is useful for building a repeatable routine:
- Log salinity (ppt), temperature, alkalinity (dKH), nitrate/phosphate (mg/L)
- Add notes like “drip acclimated 45 min” or “placed low, ramp lights 10% weekly”
- Set reminders for QT checks, coral inspections, and follow-up testing
Shrimpy (that’s me) can help you interpret trends and spot “quiet” instability before it becomes a problem.
Common mistakes beginners make (and easy fixes)
Skipping quarantine
Fix: If full QT feels like a lot, start with a simple observation QT (heater, sponge filter, hiding places). The habit is the win.
Rushing acclimation or chasing numbers
Fix: Match temperature and salinity, then move the animal into clean water. Avoid long bucket sessions in questionable shipping water.
Adding too many animals at once
Fix: Add slowly. Wait at least 1–2 weeks between additions in many beginner systems, longer if nutrients/ammonia swing.
Overdipping / wrong dip for the problem
Fix: Follow label directions exactly. Dips reduce pests; they don’t replace inspection and quarantine practices for corals.
Placing coral under full light immediately
Fix: Start low or reduce intensity, then ramp up over weeks. When in doubt, go slower.
Quick reference: fish vs coral introduction checklists
| Step | New fish (best practice) | New coral (best practice) |
|---|---|---|
| Before purchase | Check compatibility + adult size | Check light/flow needs + space for growth |
| Biggest risk | Parasites (ich/velvet/brook) | Pests (flatworms/nudis/aiptasia) + light shock |
| Best protection | Quarantine tank (2–4+ weeks) | Inspect + dip + (ideal) coral quarantine |
| Acclimation focus | Temp + salinity match; avoid bag water in display | Dip + rinse; gradual light/flow acclimation |
| First 72 hours | Eating, breathing rate, aggression management | Polyp response, tissue health, no pests |
| Key testing | Ammonia/nitrite = 0 mg/L | Alk stability (dKH), nitrate/phosphate stability |
New fish checklist
- Confirm display/QT is stable (temp, salinity, 0 mg/L ammonia/nitrite)
- Quarantine/observe 2–4 weeks if possible
- Drip acclimate to match salinity (often 30–60 min)
- Keep lights low on introduction day
- Use acclimation box if aggression is likely
- Do not add bag water to the display
- Monitor closely for 72 hours; test ammonia
New coral checklist
- Inspect under good light (base, underside, crevices)
- Dip per label instructions
- Rinse in separate container(s)
- Start low light / moderate flow; ramp over 1–3 weeks
- Secure mount; prevent falls
- Monitor tissue and pests daily for the first week
- Track alkalinity (dKH) after adding stony corals
FAQ
Should I quarantine every saltwater fish before adding it?
Yes, it’s the safest approach. Even healthy-looking fish can carry ich or velvet. A simple observation QT for 2–4 weeks greatly lowers risk.
How long should I drip acclimate a new reef fish?
Often 30–60 minutes is enough, focusing on matching salinity. Avoid very long acclimation if shipping water quality is poor.
Can I add a fish directly to the display tank if it looks healthy?
It’s possible, but it increases risk of introducing parasites. If you skip QT, you’re accepting the chance of needing a major fallow period and treatment later.
Do I need to dip every coral before placing it in my reef tank?
Strongly recommended. Dips help reduce pests like flatworms and nudibranchs. Still inspect carefully because eggs can survive.
When should I turn the lights off after adding a new fish or coral?
For fish: dim lights or keep them off for the rest of the day to reduce stress.
For corals: avoid sudden high intensity—either start low in the tank or reduce intensity/photoperiod for a few days, then ramp up slowly.
How soon can I add another fish or coral after the last one?
Often 1–2 weeks is a beginner-friendly pace, assuming parameters remain stable (especially ammonia/nitrite = 0 mg/L) and everyone is eating/looking normal. Slower is safer in small or new tanks.
Conclusion
Successful introductions are mostly about avoiding surprises: stable water, careful acclimation, quarantine for fish, and inspection plus dipping for corals. Go slow, change one thing at a time, and watch the first 72 hours closely.
If you want an easy way to stay consistent, log each step in Reef Buddy—parameters (ppt, dKH, mg/L), acclimation time, placement notes, and follow-up checks. And if you’re unsure what a trend means, ask Shrimpy inside the app for practical next steps tailored to your tank.