Can they be acclimated to fresh water?

[dagmarsawayn]

Has anyone tried this?

[Paulzie67]

I've wondered the same thing but figure "Someone" must have tried

[Vorteil]

Cannot be acclimated to FW

[xyang074]

I believe there is someone in this forum or another who wanted their opae to stop breeding, so they gradually did water changes to turn their brackish opae tank to a freshwater tank. They were successful with turning their tank into a freshwater tank and with getting the opae to stop breeding, but I'm not sure how it effects their lifespans; nor did the poster ever update on the condition of their opae. To answer your question, yes, it has been tried. I think it's a very risky thing to do.

[Vorteil]

I gotta call BS on successfully converting to FW. There's been studies done by Dr. Scott Santos that stated cannot survive in FW or full SW. Hypothetically speaking if this were possible these would be an ideal shrimp to keep in FW.

[xyang074]

In my initial research before obtaining some opae, I came across a comment somewhere in a forum where they wanted their opae to stop breeding, so they gradually did water changes to turn their brackish opae tank to a freshwater tank. They were successful with turning their tank into a freshwater tank and with getting the opae to stop breeding, but I'm not sure how it affects their lifespans; nor did the poster ever do an update on the condition of their opae in the prolonged freshwater environment, or if they were able to survive for a prolonged amount of time in the converted freshwater tank. To answer your question, yes, it has been tried. Mustafa has also tried acclimating some opae into a freshwater setup and noted how the opae showed signs of major distress. I have not read of any stories of anyone successfully having opae in a freshwater environment for a prolonged amount of time. I think it's a very risky thing to do, and if it were tried it risks the lives of the opae.

*Edited for clarity and added an idea*

[xyang074]

I actually decided to look deeper into this topic. My school gives us access to many research papers. There have been many instances in studies where adult opae ula have been introduced and have shown to "tolerate" freshwater environments. There are some papers that state that adults are "freshwater adapted".

To quote the paper Developmental Transcriptomics of the Hawaiian Anchialine Shrimp Halocaridina rubra Holthuis, 1963 (Crustacea: Atyidae), the author states, " The Hawaiian anchialine atyid Halocaridina rubra (Holthuis 1963) is an exemplar of this clade, with adults tolerating salinities ranging from fresh (e.g., 0‰) to hypersaline (e.g., 50‰) waters via a novel mechanism of chronically upregulated osmoregulatory processes, thus leading H. rubra to be the strongest known osmoregulator among the Crustacea (Havird et al. 2013, 2014a). Notably, H. rubra larvae do not tolerate freshwater and lack gills capable of ion transport until the post-settlement juvenile stage or later."

There is another paper, Reproduction and Development in Halocaridina rubra Holthuis, 1963 (Crustacea: Atyidae) Clarifies Larval Ecology in the Hawaiian Anchialine Ecosystem, that states that it is possible for opae ula larvae to develop at very low salinities. "Of the 25 larvae allocated per treatment, 22 (88%) and 18 (72%) survived and underwent metamorphosis into juveniles at 15‰ and 32‰, respectively, while only three (12%) did so at 2‰."

What this means is adult opae ula are the strongest species among crustaceans when it comes to being able to maintain osmoregulation (the regulation of osmotic pressure in regards to an organism's body). Opae ula larvae on the other hand do not have this ability, therefore, opae ula larvae will die in freshwater. However, they are able to metamorphize at salinities as low as 2 parts per thousands, although at a 12 percent survivorship rate.

I bet if a dedicated breeder/scientist had all the time and patience in the world, they would eventually be able to evolve a variant of Halocardina rubra into a freshwater species by means of introducing tens of thousands of generations of opae ula to lower and lower levels of salinity to eventual freshwater. Kind of like that fruit fly experiment.

My advice is if you are considering a freshwater tank, you should not get opae ula and get some neos. Opae ula are meant to, and only thrive in brackish water.

Hope that helps.