Q. I would like to set up a small tank for the red volcanic shrimp with the proper salinity of 1.014 but I am wondering how long they could survive in reef conditions — salinity 1.025? Is it the case that they could live in a reef tank but would not reproduce? Or will they die soon after being added to that tank? They are for food but it would be best if they could live in the reef tank. If they can survive in reef conditions I would like to put them in my refugium as well.
A. You are referring to the Hawaiian red shrimp Halocaridna rubra. As you probably already know they are found in brackish conditions of 1.0145 to 1.0168 in coastal anchaline ponds here on the Big Island in Hawaii. (They are found on other Polynesian islands too, but rarely).
They can and do survive in salinities common to reef conditions ranging from 1.022 to 1.026 but it is tricky to acclimate them to these conditions. It requires a very slow acclimation that should take place over several days, and even then some will not make it. Others will survive for a while and then with the smallest change in environmental conditions such as temperature or a nitrate bump they will seem to "suddenly die." However, there will be some that survive everything and end up surviving for years in your tank ... but very few. I would guess probably less than 5 percent, so be prepared to lose a lot.
I do not think these survivors will breed but they may. These shrimp are probably the worst breeders that I have ever seen. The fecundity is so low that you will be lucky, even in optimum conditions, to get more than 5 or 6 offspring per spawn. They seem to only spawn 5 or 6 times a year as well. To make matters worse, they are nocturnal, so if you are curious as to whether or not they are breeding successfully, you will have to check on them at night. They are very sensitive to light so they will scatter as fast as they can when the light switch goes on. And then there is the fact that I have yet to see a marine creature that does not consider these shrimp to be as good as apple pie ... and they will chase them down aggressively. The seahorse especially. I have watched a seahorse literally spend two hours in the same spot, bent over looking into a hole with his snout way into the hole waiting for that darn shrimp to make the slightest movement so he can suck it up as quick as can be!
Because the shrimp make such good prey items for any predator I would recommend the refugium if you decide to try your luck with the reef system and higher salinities. That way you can at least monitor the population without having to wonder how many were eaten versus how many just did not make the acclimation. The best place though, in my mind, to hold these red shrimp, is in a separate vessel with the proper salinities that they are found to thrive in naturally.