How to Dip and Inspect Corals Before They Go In
- Nov 11, 2025
- 6 min read
Updated: 5 days ago
Assume every new frag is carrying something. That is not pessimism, it is arithmetic: corals are grown in crowded systems, shipped in bags of their own water, and handled by several people before they reach you. A coral dip is the twenty minutes that stands between a frag pack and a year of chasing flatworms across your rockwork. The procedure itself is not complicated, but it is easy to do badly, and a rushed dip gives false confidence rather than protection. Here is the routine we follow on every coral before it goes anywhere near an established display.
What a coral dip actually removes, and what it misses
A dip is a chemical irritant, not a sterilizer. Iodine-based and commercial reef-safe dips make conditions unpleasant enough that soft-bodied hitchhikers let go: acropora red bugs, monti-eating nudibranchs, red planaria and various worms release their grip and fall to the bottom of the container. That falling-off is the whole mechanism, which is why agitation matters more than soak time.
What a dip does not do is kill eggs. Nudibranch and flatworm egg clusters are laid on the underside of the frag and inside the drill hole of the plug, and they shrug off a normal dose. Hard-shelled pests are similarly stubborn, so vermetid snails and small aiptasia usually survive and need mechanical removal. Bacterial and viral problems are outside a dip's reach entirely.
Set your expectations accordingly. A dip buys you a clean starting point on the visible pests, and inspection plus quarantine handles everything the dip cannot reach. Treating the dip as the whole defense is the most common error we see, and it is why people who dip religiously still end up with an infestation eight weeks later. The dip is step one of three, not the whole procedure.
Setting up a coral dip station before the box is opened
Have everything ready before a single bag is cut. You want three shallow containers, ideally white or clear so pests are visible against the bottom: one for the dip solution, and two for rinsing. A turkey baster, a pair of bone cutters or nippers, tweezers, a bright light and reef-safe glue or putty complete the kit. Doing this after the corals arrive means working while they sit in cooling shipping water.
Fill all three containers with water from the destination system, not from the bag and not from a mixing barrel that has not been checked. Matching salinity and temperature keeps the coral from taking two stresses at once, and a small heater or a warm room helps if the containers will sit for a while. Dose the dip container to the label, because the concentrations on commercial dips are not interchangeable between brands.
Temperature-acclimate the sealed bags for about fifteen minutes first, then work one coral at a time. Shipping water never goes into the display, the dip water never goes back into the system, and the rinse containers get refreshed if they start looking cloudy. Keeping a coral dip station tidy sounds fussy until the evening a single careless pour undoes the work on every other frag in the box.
Working through the dip, agitation and rinse in order
Contact time is where people improvise, and improvising is what damages corals. Most commercial dips specify five to fifteen minutes, and that range exists because concentration varies between products. Longer is not safer. An extended soak stresses tissue, and a bleached or receding frag two days later is often a dip that ran twice as long as the label allowed rather than a pest that got through.
Agitation is the part that does the work. Every two or three minutes, use the baster to push a firm stream of dip solution across the base, into the drill hole and under any overhanging tissue, then swirl the container gently. Pests that have already released will lift off the coral and settle at the bottom, which is exactly where you want them and exactly why a plain white container earns its place.
Rinsing matters as much as the dip. Move the frag through both rinse containers with a gentle swirl in each so no dip solution rides into the display or the quarantine tank on the plug. Work through the sequence in this order every time:
Temperature-acclimate the sealed bag for about fifteen minutes.
Open the bag over a bucket and move the coral straight into the dip, leaving the shipping water behind.
Dip for the labeled contact time, usually five to fifteen minutes.
Baste the base and plug every two or three minutes and watch the container floor.
Swirl the frag through both rinse containers.
Inspect under bright light, then cut the coral off its original plug.
Glue it to fresh rock or a clean plug and place it in quarantine.
The frag plug and the base are where pests hide
Inspection is the step most people skip, and it is the one that catches what the dip left behind. Hold the frag under a bright light and look at it from underneath, using a magnifier or the macro mode on a phone. You are looking for small ovals or spirals of eggs, tiny white or brown snails, tissue that does not match the coral, and any movement at all around the edge of the base.
The plug itself is the problem. Frag plugs have a rough surface, an undercut mushroom shape and a hole through the stem, and that geometry shelters eggs, worms and juvenile snails from both the dip and the baster. Once a plug goes into a display it becomes almost impossible to inspect again, and it usually ends up wedged in the rockwork where nothing can be checked.
So retire the plug. Nip the coral free above the base with bone cutters, discard the original plug, and glue the frag to fresh rock or a clean plug of your own. It costs a minute and removes the single most likely vector in the whole process. Choosing well before this stage helps too, and our notes on picking healthy coral frags cover what to look for at the point of purchase.
Quarantine after the dip is what makes the effort count
Quarantine is where eggs get caught. A separate small system with its own heater, a modest light and some flow will hold new corals for four to six weeks, which is long enough for any surviving egg cluster to hatch and reveal itself while the coral is somewhere you can treat it. The tank does not need to be pretty, and a plastic tub with a clip-on light works.
Repeat the dip once during that period, at roughly seven to ten days, because that timing catches the newly hatched generation before it can lay again. Watch the coral rather than the calendar: extension, polyp behavior, color and any tissue recession all tell you whether the frag settled or is still fighting something. Corals that look worse each day usually need a parameter check rather than another dip.
Some livestock in your display can help hold the line afterward. A few peppermint shrimp, a filefish or the right snails will keep pest populations from rebounding, and our guide to using inverts for natural pest control covers which ones are genuinely reef safe. Predators are a supplement to quarantine, never a replacement for it.
Key takeaways
A coral dip loosens soft-bodied pests through agitation; it does not kill eggs or hard-shelled hitchhikers.
Set up three containers of destination-system water before opening a single bag, and dose the dip to its label.
Stay inside the labeled contact time of roughly five to fifteen minutes, and baste the base every few minutes.
Cut the coral off its original frag plug and glue it to fresh rock, because the plug hides the most.
Quarantine for four to six weeks and dip a second time at seven to ten days to catch hatched eggs.
Frequently asked questions
Can I dip every coral the same way?
Most stony and soft corals handle a standard reef-safe dip at the labeled dose, but not everything does. Anemones should not be dipped, and non-photosynthetic corals, some gorgonians and very small or freshly cut frags tolerate it poorly. Shorten the contact time for anything delicate, watch the tissue, and stop early if the coral looks distressed.
How do I know the dip worked?
Look at the bottom of the container rather than at the coral. Pests that have released settle out, so a plain white or clear dish shows you exactly what came off. An empty container is not proof of a clean frag, though, since eggs stay attached. That is precisely why inspection and quarantine follow every dip.
What if I do not have a quarantine tank yet?
Dip and inspect thoroughly anyway, then place new corals somewhere accessible in the display rather than deep in the rockwork so you can pull them if something appears. It is a compromise, not a solution. Even a small tub with a heater and a cheap light meaningfully lowers the risk of seeding an established reef.
Work with Marine Concepts Inc
If a frag has already brought something in, or you would rather have somebody else handle acclimation and quarantine, our aquarium maintenance service covers pest identification and treatment across Chicagoland, and dips, glue, fresh plugs and healthy coral are all on the shelf at our aquarium shop, Marine Concept Supply in Wheeling, IL. Call ahead to confirm what is in stock.
Comments