Axies do not have a swim bladder unlike fish. They orientate their positions and coordinate their movements mainly through the central nervous system. Balance and fine motor control are performed by functions of the vestibular and cerebellar centres in the brain. This is further fine tuned by the lateral sensory line along the sides of the body which contains special movement, chemical and even electromagnetic receptors. Axies with balancing problems have a neurological deficit.
There are many causes of this. Sometimes direct physical trauma to the spinous or nerve regions on the body can cause inflammation and bruising. Toxicity from nitrogenous wastes or other water contaminants as well as malnutrition (Vit B defiency/anaemia) and certain pathogens like bacteria can all cause brain tissue damage. Sadly, the vast majority of neurological problems cannot be 100% cured but there are treatment options to improve the condition.
In some rare cases, impaction and constipation can present with upside down or contorted posturing. Impacted material tend to be 'solid and firm' and thus capable of causing compression. Think of a huge ball in the intestines pressing against the spinous nerves. Because axie's are soft bodied, have a 'tubular body' and their alimnentary tract runs parallel to the spine, Impacted material can press against nerves controlling the hind limbs, tail and cloaca, causing 'paresis' in the hind limbs, tail and even problems with expelling wastes.
The best treatment is to fridge like what you have been doing and if you want to take a step further, i suggest you take the axie to a vet for imaging (radiography/ ultrasonography) to detect presence of any impaction or even tumour/abscess growing internally. In the event of internal growths, prognosis will be guarded and euthanasia is an option.
