Ok, I'm gonna give it a shot.
First, I'm sure LDS, is LFS. The D is right next to F on keyboard!!
Second, yes the brine will need to be fed and they need an airline to keep alive!
But really, it's been 3 pages and over a month since the start of this thread and you still have them in the display tank.
On the very first page, Sept. 1 and 2, Meowzer told you how to set up a DT.
Why do you have sand in there. It needs to be bare bottom so you can see and remove leftover food and poop. You will have to do large daily wc to offset the ammonia, etc.
What you need to do is: siphon 10g of water from your display into your hospital tank. add the airline and a couple of fake anything saltwater safe for your horses to hitch on. If you have anything in your display with a sponge on it, you can add the sponge to add bacteria. Then get those horses in there!!
Also, on the first page, Ann described the fw dip. She said when you finished it, NOT to put your horses back in display tank, as it would be full of the parasites you just removed. You were to put them into the hospital tank, immediately!! So, every time you have fw dipped these little guys, you turned around and exposed them to the same parasites you just removed.
These are just 2 examples of why people are getting frustrated with you. I could go on for a while about the advice you have ignored. I'm sorry to sound mean, but you really need to reread this thread from the beginning and realize that all the advice you need is here. You just need to follow it!!