To understand swim bladder you really have to understand how the swim bladder air sacs work inside the fish to keep it upright and how important these sacs' health is for the bouyancy of a fish. The swim bladder is made up of 2 parts. Imagine one of those long shaped party balloons - a white one -and that someone has twisted it round in roughly half and it has remained like that. Then, imagine the whole uneven 2 bubbled shape covered in a microscopic mass of tiny threadlike blood vessels, rather like biology pics of the human eye you may have seen, and given a small pump pipe to control the balance of gases retained.

These 'sacs' are very tightly packed into the abdomen of the fish. The shape/design of them suits the elongated body of a comet/common fish much, much better. In a fancy fish the 2 lobes of the air bladder/swim bladder are compressed in a much tighter space. Anything that affects the space inside the fish is going to affect the air sacs ability to balance the fish and the vascular gas exchange support network neccessary to maintain balance.

So fish that are showing signs of "sbd" can be suffering from a huge multitude of different problems. Any of these could be responsible for damaging the efficiency of the 2 air sacs to constantly expell and take in air/gases to maintain that continous balance of correct airflow that gives a fish its amazing ability to remain upright and float and swim.

Some of the things that most commonly affect airsac control are these:
Bad water: any of the common toxins like ammonia/nitrites/pH problems and high bacterial load
Over feeding: which can inflate the intestinal tract squishing and crowding out the airsacs above.
Eggs: a fish that is full of eggs -the eggs can put pressure on the sacs causing malfunction.
Infection: viral,bacterial and parasitic- causing inflammation of organs or build up of visceral fluids inside the fish.
Constipation and gas: A diet of solely processed commercial food can pack up the gut with air and cause bloat which squeezes the airbladder. Wheat and soy in processed foods require for digestion, the production of an enzyme that also produces some gases that create bubbles in poop and indicate gas build up. These fish should be either fasted or overfed for a few days or permanently if severe- on non processed foods to eliminate the gas.
Airbladder malfunction: sometimes the tube connecting the airsacs, the physostome, gets blocked, temporarily or permanently. In a worst case scenario water can enter and fill the swimbladder causing total malfunction. The fish will flipover. This is true "swimbladder disease".
High nitrates: these can affect the vasodilation capacity of blood capillaries- this one reminds me of how a fatty diet can affect the ability for people's blood vessels to transport blood to the human heart...arteries and vessels clog.
Gulping air: lack of oxygen, nitrite poisoning, plunging pH and parasites will have the fish piping for air. Gulping air deregulates vascular air flow and causes balance problems as th GI tract swells with air. Fish should not be at the surface.
Overuse of antibiotics: after use of antibiotics fish will have less available bacteria inside to help regulate vascular activities that support a healthy balance. The more antibiotics and medications we have used on a fish, the more likely it becomes they will weaken the fishes inner system. Longterm use of antibiotics can also damage the kidney causing bloat as the fish becomes unable to expell waste efficiently.

So, the question of siwmbladder is not an easy one and definitely requires closely observing and eliminating each possibility.

If you are now thinking eggs are the culprit for misaligning the airsacs, you can similate male nudging/breeding behavior by extremely gently stroking the female's belly under water which can help. Then immediately do a very large water change (matched temp and pH). This can help recreate 2 'environmental' factors thought to help eliminate eggs.