First of all, there aren't too many places to buy wild caught any more.
Also I'm assuming they are eating frozen mysis which would indicate at worst that they are tank raised Asian imports.
There are a number of places selling true captive bred ones now, increasing the odds that you have some of those.
If it had "the bends" I would expect the body to be swollen, not just a bubble.
The great majority of seahorses are found too shallow to get the bends anyway as far as I know.
While you don't THINK the water quality to be an issue, experience has shown many of us to be otherwise.
THERE ARE NO TEST KITS AVAILABLE to hobbyists that can tell you when the bacteria potential is dangerous or that chemical imbalances within the seahorse are going to occur.
Changing the water in the display tank will improve conditions there but I doubt it will suffice to correct the already present condition of that seahorse.
Total change in a hospital tank has a MUCH better chance of success.
It's also possible that the condition is due to conditions it had before you got it if you just received it in the last few days to a week.
Unfortunately because we can't test for these problems we have to be proactive with our husbandry practices.
My Thoughts on Seahorse Keeping
