Adult Mono Argentus in Light Brackish?

[spitz006]

I am keeping mono argentus in a "light" brakish tank. The Specific Gravity fluctuates between 1.002 and 1.004. Will they thrive in this condition indefinitely or do they require full saltwater as adults?

I've googled, and most websites are saying to give them full marine as adults, but is this absolutely neccesary? Is it possible that populations of adult monos live in freshwater or light brackish waters?

 

[brackishdude]

I think the common wisdom of keeping BW fish in full marine as adults is overstated and overapplied, but may be most accurate with the monos. Some have had success on the low end of BW, I did not, but it was early in my BW fishkeeping years. I think that with clean water with a current, and in numbers sufficient to school, you've got a decent shot, assuming you've got tankmates that can't handle a higher sg. Otherwise, just add some salt!

 

[WinterAlloy]

This probably won't be very helpful to you, but I will try. Most articles that you read will instruct you start in mild brackish and work your M. argentus to seawater. IMO, most catadromous fish, the columbian cat shark for example, can do well as adults in approximately SG1.015 to seawater. Dr. Monks, believes that these Malayan Angels will do fine in SG1.012 to seawater as adults. Finally, though, I have also read an article which states that M. argentus can be acclimated to live in very mild brackish (SG1.002 to SG1.005) as an adult, but the fish needs a very hard water with a high pH of 8.0 or even higher. In the wild, young M. argentus live in low salinity water and migrate to seawater with age. Beware that some "hobbyists" (especially 1 particular big box company) say that with care the M. argentus can live up to 2 years and get up to 6". This is incorrect! M. argentus should live up to 10 years in captivity and reach 10". If said groups anticipate this, then their recomended care is more than likely inadequate. Just food for thought. Also, on the other hand, one proven method of breeding M. sebae is to increase the water density to seawater, and then each day replace a very small percentage of the seawater with freshwater. This slowly works the density down and immitates the breeding season. What ever you do, please keep us posted so that we may learn too!

 

[spitz006]

Thank you! Since I live in an area with very hard water, I'll give it a try.