Bloated Seahorse

[rayjay]

Is this a dwarf in a 6.6g aquarium?
If it is a standard sized seahorse then you will almost certainly have continual problems with it as the tank is a WAY too small for it.
Bloating can be from a female that is producing a pile of eggs and hasn't transferred them to the male yet but is due to.
It can also be due to internal gas bubble disease but usually in that case she/he would be floating.
Another cause is edema which is fluid build up due to kidney failure. When this gets bad, the seahorse will usually be on the bottom, often leaning over due to the weight.
You will probably have to treat it in a hospital tank using Diamox (acetazolamide) which usually needs a prescription.