seahorse not doing well need help asap please!!!!!

Just recently we acquired 4 sea horse from a friend that had to get rid of them immediately, we set up a tank for them but something happened and caused us to take them in before our sea horse tank had time to finish cycling so the sea horses went in our main tank. They have been in the tank for about a 3 weeks now without any problems until tonight, I caught our royal blue tang (Dory) nipping at one of the seahorses and immediately was able to get the tang away from the sea horse and watched for a while to make sure the sea horse was ok, it seemed like it was fine. About an hour later I noticed that the sea horse was sorta twitching on the bottom of my tank, and would not swim just kinda flopped on the bottom of the tank, it was also breathing very heavily, I instantly took the seahorse out of the tank and put it in a bucket of water with an air tube in there for it and under another light we have inside of an empty tank so the light wasn't directly on top of the bucket. I inspected the seahorse for damage from the tang and didnt see any damage to it, now the sea horse is hitched to the air tube and is just laying on the bottom of the bucket (which it was doing when I took it out of the tank) its breathing has slowed but it is still not swimming at all just laying there and randomly twitching (almost) in a slower rate then before. Is the sea horse sick, or could it be too stressed out from the tang, or is it on its last bit of life left? I will try to post a pic of what it looks like at this time. Any help or advice would help greatly as we do not want to lose this horse. (we are sure that it is a mated pair and it would also leave an odd number of sea horses as well as make its mate sad to lose its mate) This sea horse is a male, also I would like to add that we are also dealing with another unexpected problem that just started cyanobacteria which we are in the process of combating at this time as well.