I noticed an increase in sickness when I used the seahorse too. But maybe that's because I didn't know he was sick. Of course I was treating the other fish with him, so he should have been treated too.
I honestly have not found a positive use for him. I think it would be cool if he could mate a fish causing a random baby. Kind of like the Certain Magic FIsh, that I won't name and spoil things, but it would only affect that one fish and not the whole tank.
I've read some people say that by buying him you can store more fish in each tank. That's just not true. I can store 21 fish in each tank from the beginning.
So is there really a reason to buy him? Maybe some one from LDW could give us a hint? Please?

Marcey