Fins & Tails, Bits & Bobbers ... Vol 1-3

AQUI-S® vs. MS-222: If you are in the fish business, chances are you have used tricaine methansulfonate (i.e., MS-222 or tricaine) to sedate fish. You may have also heard about the experimental fish anesthetic AQUI-S®. We’ve used/tested AQUI-S® extensively over the past few years and would like to pass along a few tips.

Question: Are MS-222 and AQUI-S® used at the same concentration?
Answer: No. Research to gain FDA approval of MS-222 and AQUI-S® were done in different eras, and the proposed maximum allowable safe and efficacious concentration of AQUI-S® will be lower than the allowable concentrations of MS-222.

Question: So what if the concentrations of MS-222 and AQUI-S® are different?
When using AQUI-S®, more time will likely be required to sedate fish to a desired level of anesthesia. We’ve also found that fish sedated with AQUI-S® tend to require more time to recover than fish sedated with MS-222.

Question: Are there differences in how to prepare a working solution of MS-222 and AQUI-S®?
You bet. With MS-222, you can shake, pour, or scoop out the desired amount, drop it into a tub of water, stir, and you’re on your way. We recommend preparing a stock solution of AQUI-S® (which is a viscous, oily liquid) in a small volume of water before pouring it into a tub of water (for mixing instructions see AADAP Newsletter, Volume 1-1 at Such stock solution will be “milky” white. Now you can stir the contents of the tub and be on your way.

Question: Will AQUI-S® decrease the pH of water like MS-222 does?
Not to our knowledge. We’ve done many comparisons under many different environmental conditions and have found that addition of AQUI-S® does not alter the pH of water (for those of you who sedate fish in water with low buffering capacity...take note!).

Question: AADAP is in the final stages of trying to complete the efficacy technical section for AQUI-S®. What does this mean to you?
Well...we can still use any additional safety and efficacy data that you have or will be willing to generate. We encourage biologists to use AQUI-S® (even if on a small scale) on a variety of fish species under the INAD and submit data to us.

Question: For which fish species/life-stages are AQUI-S® data needed?
We’ll take AQUI-S® data for any and all fish species/life-stages. Chances are that, even if we have a sufficient quantity of data for a specific fish species, conditions under which you sedate fish will be different than conditions under which we (or others) sedated the same species. We’re on the prowl for a higher quality data package, which should include fish species and size sedated, AQUI-S® target concentration, description of the desired level of anesthesia, times to and from the desired level of anesthesia, water temperature, dissolved oxygen concentration, behavior of fish on initial immersion into a solution of AQUI-S® and on recovery in freshwater, and mortality attributed to exposure to AQUI-S®.

Question: Is AQUI-S® intended to replace MS-222?
Unequivocally, no! Tricaine has been, and will continue to be, a very useful aquaculture and fisheries management tool. However, the 21-d withdrawal period often legally precludes returning treated catchable-size fish to public waters. Our hope is that AQUI-S® will ultimately be approved with a zero day withdrawal period.

Southern Regional Aquaculture Center Fact Sheets: The Southern Regional Aquaculture Center (SRAC) is one of five USDA Regional Aquaculture Centers whose operations and activities are coordinated by USDA’s Office of Aquaculture. The Regional Aquaculture Centers encourage cooperative and collaborative research and extension education programs in aquaculture that have regional or national application. The SRAC has produced a series of Fact Sheets, many of which can be quite useful to those administrating approved and investigational drugs. The SRAC Fact Sheets can be found on their website at: Of particular interest may be those under the following categories: treatments ( ) and diseases ( ).
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LAST UPDATED: 16-Jan-2013