Quarantine Checklist for Saltwater Fish

Set up a separate 10 to 20 gallon tank for small fish like clownfish and gobies, and 20 to 40 gallons for tangs, angelfish, or multiple arrivals. A bare bottom makes it easier to siphon waste, monitor feces, and keep ammonia under control during treatment.

Seed a sponge filter or ceramic media in your display sump for at least 2 to 4 weeks before use, then move it to quarantine when needed. This gives immediate biological filtration, which is especially important because many marine fish arrive stressed and produce significant ammonia in the first 48 hours.

Aim to start quarantine near the fish store or shipping water, often around 1.020 to 1.025 SG and 76 to 78 F, then adjust slowly over several days if needed. Matching parameters reduces osmotic stress, which is a major trigger for disease outbreaks in newly imported marine fish.

Keep temperature stable within 76 to 78 F and avoid daily swings greater than 1 F. Marine fish under treatment often stop eating when temperature fluctuates, and some medications become harder to manage when water conditions are unstable.

Use several pieces of PVC in sizes that let fish wedge in without scraping their fins or scales. Unlike live rock, PVC does not absorb copper and still gives shy species like wrasses, blennies, and angelfish a secure refuge.

Many quarantine losses happen from jumping, especially with wrasses, firefish, dartfish, and grammas. Cover all openings around hang-on-back filters, airlines, and cords because startled fish can launch through surprisingly small gaps.

Keep ammonia at 0 ppm and treat any detectable level as urgent, particularly in small quarantine tanks. Use a liquid test or ammonia alert badge, and be ready with water changes or an ammonia detoxifier if feeding increases waste faster than the biofilter can respond.

Target pH around 8.0 to 8.3 and alkalinity roughly 7 to 9 dKH to prevent added stress during acclimation and medication. Poor gas exchange and low buffering are common in small quarantine systems, so surface agitation matters.

Use fresh RO or RODI water to replace evaporation so salinity stays steady, ideally within 1.023 to 1.026 SG for most marine fish unless you are intentionally matching lower source salinity. In small tanks, even a little evaporation can shift SG enough to stress delicate arrivals.

Prepare backup saltwater at matching temperature and salinity before the fish arrives. Plan on 10 to 25 percent changes as needed, especially when feeding heavily, treating with medications that suppress biofiltration, or quarantining messy eaters like puffers and triggers.

Run an air stone or ensure vigorous surface movement because copper, formalin, and antibiotics can reduce oxygen availability or increase respiratory stress. Fish showing heavy breathing in quarantine need immediate evaluation of both dissolved oxygen and disease symptoms.

Use dim ambient light or short photo periods to help fish settle after shipping. Bright lighting often increases pacing, hiding, or refusal to feed in species such as tangs, butterflyfish, and anthias.

Check for torn fins, cloudy eyes, excess mucus, flashing, rapid breathing, white spots, gold dusting, lesions, and pinched bellies. Early notes on visible symptoms help you distinguish shipping stress from parasites like Cryptocaryon, Amyloodinium, or flukes.

Float bags to equalize temperature, then measure salinity and only prolong acclimation if the difference is significant, such as more than about 0.002 SG. Long drip acclimation in shipping water can backfire because pH shifts may make accumulated ammonia more toxic.

Shipping water may contain elevated ammonia, pathogens, and medications from the exporter or retailer. Net or transfer fish with a specimen container and keep the contaminated water completely out of your system.

Try species-specific starter foods such as frozen mysis, enriched brine, LRS-style blends, nori for tangs, or small pellets for captive-bred fish. Early feeding response is one of the best indicators of whether a new marine fish is stabilizing or declining.

Count gill movement if a fish seems stressed and look for head-up hovering, laying on the bottom, clamped fins, or hanging near flow. Fast breathing can point to velvet, gill flukes, ammonia irritation, or inadequate oxygen long before external spots appear.

A peaceful goby and a new dottyback or trigger often do poorly together in close quarters. Use dividers or separate systems when needed because aggression in quarantine can suppress feeding, increase injury, and complicate disease diagnosis.

Have a clear protocol before fish arrive so you are not improvising under stress. Many marine hobbyists either observe for 2 to 4 weeks with treatment only if symptoms appear, or proactively treat for common threats like ich, velvet, and flukes.

If using copper, verify therapeutic concentration with a compatible test kit because chelated and ionic products are measured differently. Underdosing may fail against velvet or ich, while overdosing can suppress appetite and harm sensitive species like wrasses and dwarf angels.

Increase copper over 48 hours or according to the manufacturer to reduce shock, especially for newly shipped fish. This approach often improves feeding compliance while still reaching an effective level quickly enough for high-risk diseases.

Flukes are common on marine fish and often show up as flashing, cloudy eyes, excess mucus, or heavy breathing without classic white spots. Many hobbyists run one to two praziquantel treatments spaced according to the product instructions, with strong aeration during use.

Have a food-safe bucket or spare tank, heater, and air stone ready if a fish crashes, needs a freshwater dip, or requires non-compatible medication. This prevents panic and avoids mixing treatments that should not be combined in the main quarantine system.

Porous materials absorb copper and make therapeutic levels unstable, while carbon removes many medications from the water. Bare-bottom treatment tanks are easier to keep at target concentration and much easier to test accurately.

Record whether spots increase or decrease, whether respiration improves, and exactly when each medication dose was given. Consistent notes prevent guessing and make it easier to complete the full course instead of stopping too early when symptoms briefly improve.

Anthias, mandarins in training, butterflyfish, and recently imported wrasses often do better with 2 to 4 small feedings rather than one large feeding. This improves recovery while limiting nutrient spikes that can overwhelm a quarantine biofilter.

Rotate frozen mysis, finely chopped seafood, quality pellets, and algae sheets for herbivores to restore energy reserves. A fish that eats only one emergency food in quarantine may still struggle once moved into a competitive reef or FOWLR display.

Do not move a fish that only pecks sporadically or eats under very specific conditions. Consistent, confident feeding is one of the strongest signs that the fish is ready to handle social pressure and different flow patterns in the display tank.

A practical minimum is often 2 to 4 weeks for observation, with longer timelines if treatment was needed or symptoms appeared late. Many saltwater diseases have life cycles that can make fish appear normal for several days before signs return.

Bring quarantine water into line with the display over several days so the final move is low stress, especially if the store kept fish at 1.020 to 1.021 SG and your display runs 1.025 to 1.026. Sudden parameter jumps can trigger setbacks even after a successful quarantine.

Cross-contamination defeats the whole purpose of quarantine, so never share wet tools between quarantine and display systems. Color-code or label equipment clearly to avoid accidental transfer of parasites or medication residue.

Once the fish has moved out, clean equipment, rinse thoroughly, and let the system dry before storing or restarting. Dry-out periods and proper cleaning reduce the risk of carrying pathogens from one batch of fish to the next.