I agree with the above they need brackish when young, and actually do best in full strength seawater as adults.
If it were me, I'd add 3 lbs of sea salt mix, immediately per every hundred gallons, and gradually add another 3 lbs per hundred gallons as they grow, sea water is about 35 lbs per hundred gallons (maybe more) so adding 3 to 6 is fairly light weight (wimpy) on the salt addition, but it might help with the infections as a starting point.
If the other fish are totally fresh water, then returning them is your best bet.
Although Mono sebae, is touted to be fresh water, they tend to only spend the early part of their life in fresh water, moving to estuaries and mangroves as adults that can be very brackish. They tend to be prone to disease in in fresh water (especially soft fresh water) . If the pH of your tap water is above 8, with high alkalinity, and high conductivity, there is a chance they may remain healthy.
But beyond Mono's, it seems most species, like scats, archers, and some gobies, do OK for a while in fresh water, but even they tend to move to brackish estuaries, or straight sea water as adults.
I take most species profiles that claim these type fish will be happy in fresh, with a grain of salt.
Sorry for the bad pun.
But beyond Mono's, it seems most species, like scats, archers, and some gobies, do OK for a while in fresh water, but even they tend to move to brackish estuaries, or straight sea water as adults.
I take most species profiles that claim these type fish will be happy in fresh, with a grain of salt.
Sorry for the bad pun.
