Acclimating Marine Invertebrates and Corals
Why invertebrates need slower salinity, temperature and pH matching than fish, how drip and light acclimation work, what coral dips can and cannot remove, and why quarantine matters.
Why invertebrates are acclimated differently from fish
Most marine invertebrates are osmoconformers: the concentration of their body fluids follows that of the surrounding water. Bony fish, by contrast, are osmoregulators that actively control their internal salt balance. Wikipedia notes that stenohaline osmoconformers such as echinoderms (sea stars, brittle stars, urchins) survive only within a narrow salinity range. A change in salinity that a fish can tolerate may therefore harm a sea star or shrimp. A 2026 review in Conservation Physiology on ornamental shrimp in the aquarium trade adds that the osmoregulatory capacity of ornamental shrimp is still largely uncharacterised.
Fish and invertebrate protocols also differ in which treatments are possible. UF/IFAS Extension describes copper and hyposalinity (reduced salt concentration) as standard bath treatments for marine fish parasites. It warns that most invertebrates are highly sensitive to copper and will not survive a copper treatment, so invertebrates must be removed before copper is used. As a result, fish quarantine often relies on treatments that would kill corals, shrimp and snails, and the two groups cannot share a treatment tank.
Matching salinity, temperature and pH
The Conservation Physiology review gives a typical salinity of 34–35 for tropical marine aquaria and notes that shippers try to keep transport water at the same salinity as the holding system. While the animal is in transit, water quality can change: ammonia and carbon dioxide build up, pH and temperature become unstable and dissolved oxygen falls. The goal of acclimation is to bring the animal from the bag water to the display water slowly enough that it does not experience a sudden jump in any of these values. Measuring salinity accurately is covered in the separate salinity and specific gravity guide.
- Temperature: float the closed bag in the tank or quarantine system so that its temperature slowly matches the tank water.
- Chemistry: move the animal and its water into a clean container and slowly add tank water so that salinity, pH and alkalinity change gradually.
- Transfer: move the animal into the tank and throw away the mixed water. Bag water collects ammonia during shipping, and Reef Builders notes that when the bag is opened and carbon dioxide escapes, pH rises and more of the ammonium turns into toxic ammonia.
Drip acclimation for invertebrates
In drip acclimation, tank water runs through a thin tube with a restricted flow into the container holding the animal, so the water mixes over a long period. A Reef Builders guide describes a drip slow enough that the container volume doubles or triples over two to three hours. Reef Builders editorial pieces stress slow dripping for sensitive groups: cleaner shrimp (Lysmata) are very sensitive to sudden changes in water parameters, and some serpent stars can be stressed to the point of death if the drip is too fast. For corals, a separate Reef Builders guide recommends a couple of hours of drip acclimation, and four hours or longer when the destination tank has a much higher alkalinity than the shipping water. No peer-reviewed drip rate exists for most traded invertebrates, so these durations are hobby guidance, not tested limits.
Light acclimation for corals
Zooxanthellate corals rely on symbiotic algae (Symbiodiniaceae) in their tissue. When these symbionts are stressed, the coral can bleach by losing them. Research setups acclimate coral fragments to new lighting before experiments. One 2023 study in Toxics matched the spectrum and intensity of the holding light to the test light in order to prevent light-induced bleaching. Another study allowed wild-collected corals a one-month acclimation period to the facility's flow, temperature and light. A 2025 experiment on Acropora divaricata found more severe bleaching under unshaded light than under 30% shade when the water was also warm, which shows that light and heat stress add up. In practice, a new coral is placed at lower light first and moved to brighter positions over time. Reef Builders also notes that dipped corals tend to bleach more than untreated ones, which is another reason to bring them up to full light gradually.
Hitchhiking pests
New corals and live rock can carry pests that are hard to see and hard to remove later:
- Acropora-eating flatworm (Prosthiostomum acroporae, formerly Amakusaplana acroporae): a polyclad flatworm that can kill whole Acropora colonies in aquaria. Its cryptic colouring and small size make it easy to introduce on coral. A 2026 study found its DNA in aquarium water even when no visible signs of infestation were present.
- Montipora-eating nudibranch (Phestilla subodiosa): described in 2020 from aquarium-traded Montipora fragments; aquarists have reported it as a prolific pest for about two decades.
- Aiptasia anemones: often arrive on live rock, sting corals, and regrow from fragments left behind after removal attempts (Wikipedia).
- Others that Reef Builders lists: Majano anemones, predatory Asterina sea stars, vermetid snails, Euphyllia-eating flatworms and Goniopora-eating nudibranchs.
Dipping corals
A coral dip is a short bath in treated seawater that is meant to dislodge pests before the coral reaches the display tank. Peer-reviewed evidence exists for a specific pest and coral pairing: Barton and colleagues (Aquaculture, 2022) found that one-hour immersions in the anthelmintics levamisole or praziquantel, followed by shaking in seawater, removed more than 90% of Acropora-eating flatworms from Acropora millepora fragments, with no effect on growth or bleaching over four weeks. That result does not set a dose for other corals or pests. Hobby dips with other ingredients, such as iodine-based or hydrogen-peroxide solutions, have no validated concentrations or durations across coral groups.
Quarantine and inspection
UF/IFAS Extension advises quarantining marine plants, invertebrates (including shrimp, clams, corals and live rock) and substrate that may have been in contact with infected fish before adding them to a system. These items can carry the encysted stages of Cryptocaryon irritans, the cause of marine white spot disease, even though they are not hosts themselves. For corals, Reef Builders editorial practice is to remove frags from their plugs or rock, which can hide pests and eggs, to inspect them under a blacklight for eggs and damaged tissue, and to hold them in a quarantine tank under reduced light before adding them to the display. The 2026 flatworm study notes that infestations are often noticed only at a late stage, so repeated inspection during quarantine matters more than a single dip.