I've only experienced it once in about 12 years but I used Diamox to treat at that time.
However, the seahorse survived and healed from what I could see, but it died anyway about 8 months later. I have no way to know if it was from the GBD or from the treatment or if it was something new.
It's my belief that GBD is caused by water quality and at the time I had some health problems and wasn't up to my normal husbandry so it was possible.
Personally I like to change water more often than weekly when I vacuum out the tank to remove uneaten food and detritus so bacteria can't get a hold in the decaying material.
IMO, the water quality issue is paramount to seahorse long term health, and if husbandry isn't sufficient, the quality gradually gets worse until sometimes it's too late for the seahorses. It may take anywhere from a few months to over a year, and when it happens we aren't aware that it has been a long term degradation rather than something just recent that we automatically think of.
I don't believe that the one water change in itself caused the problem.
