Just to recap, so are fish unaffected by acceleration because they are floating in a liquid?

If so, why don’t they fill fighter pilots cockpits with water (apart from the fact they would drown)?

Observation:
Those fish are all the same way up. Why is that in (next to) zero gravity?

No-one’s said they are ‘unaffected’.

The pressure in the water increases. And their blood would flow down to their.. er.. belly.. just the same as with fighter pilots.

Why is that in (next to) zero gravity?

It’s not an answer, but it’s not zero gravity. It’s nearly the same as on earth.

The acceleration acts only on the water not on the fish so as long as the fish is neutrally bouyant (or able to maintain bouyancy) then it will feel little in the way of an effect.
Maybe I’m missing something but why look at the effects of weightlessness on fish when they inhabit a zero gravity habitat on earth?

The acceleration acts only on the water not on the fish so as long as the fish

Rubbish.

Maybe I’m missing something but why look at the effects of weightlessness on fish when they inhabit a zero gravity habitat on earth?

Floating is not the same as zero gravity. Take a hot air balloon ride, then pour a glass of champagne, see which way the drink falls.

The water around the fish supports it, but gravity still affects it.

The acceleration acts only on the water not on the fish so as long as the fish

Rubbish.

Ok – explain this please.

Maybe I’m missing something but why look at the effects of weightlessness on fish when they inhabit a zero gravity habitat on earth?

Floating is not the same as zero gravity. Take a hot air balloon ride, then pour a glass of champagne, see which way the drink falls.

The water around the fish supports it, but gravity still affects it.
Not sure what your point is? Of course the chanpagne would fall into the glass gravity still acts on the champagne as air is not a dense medium. The effect of gravity on water pressure is minimal compared to water depth. You cannot compress water so along as the tank that holds the water that holds the fish accelerates at the same speed as the rocket the effect on the fish is tiny. If the fish were forced to the bottom of the tank there is no way they would survive the journey into space let alone swim around to have experiments performed on them.

as air is not a dense medium.

So if it was dense, it would some how be a gravity shield?

The effect of gravity on water pressure is minimal compared to water depth.

so what causes the increase in pressure when you go deeper?

As has been said, gravity is much the same in orbit as it is on earth.

What will happen if an absent minded astronaught knocks over the fish bowl and spills the water and fish into a giant floating orb of water…..will the fish continue to swim around inside the blob?

Do any of the fish know how to drive the tank?

Maybe I’m missing something but why look at the effects of weightlessness on fish when they inhabit a zero gravity habitat on earth?

?
There is still gravity under water. Drop a brick into a pond to check if you wish.
The brick will fall more slowly than it would through air as the drag casued by the water is more than that casued by air but it will still fall. Some stuff which is less dense than water floats in the same way as stuff which is less dense than air floats in air. Helium baloons are not unaffected by gravity, they are just less dense than air and so make their way to the top in the same way that wood is less dense than water and makes it way to the surface of water, wood is not imune to gravity.
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Anyway, back to the OP.
To apply my logic above has anyone looked at what happens to stuff which was in the air inside a spaceship when it takes off? Does all the dust for example make it’s way to the back (bottom?) of the rocket or does it remain stationary within the air? Does dust/air serve as a suitable (and observable) analogy for fish/water? It might be a better model is cannot power itself to remain near the top as a fish can.

Dunno, but the Pilot Fish can fly the spacecraft.

Observation:
Those fish are all the same way up. Why is that in (next to) zero gravity?

Id guess the tank is fully sealed with a forced flow from front to back of the tank. Few reasons for that, to maintain a constant flow of oxygenated water for them to breath and ensure there are no ‘pockets’ of dexoygenated water, to get rid of any fishy ‘waste’ products, to ensure no big air-bubbles form which the fish could float into and suffocate.

Do any of the fish know how to drive the tank?

^ genius!