Dr Karl

Your fish?

F-I-S-H?

The things in the tank?

Through the air, you and I can see a vast distance and fish can depending on how well focused their eyes are.

You begin to have trouble seeing through air when you're looking through, say, maybe 50 or 100 kilometres of it, like the astronauts...

in the International Space Station 400 kilometres up.

In water, you can normally see maybe 20, 30 metres and then it gets too opaque for both us and fish.

There are some fish that hover around on the surface and they have got a split eye where they've got one set of optics for above the water and one below.

What sort of fish are they?

Oh, my gosh.

Don't people actually pay money to have fish eat the dead skin off their feet or something?

Yeah, you've got to be so careful, though.

Okay, fair enough.

So how far are you from the fish when they begin to react to your physical, visual presence?

Okay, right.

And, oh, whoa, this is a good scientific experience.

And how often do you feed them?

So do they do this mainly in the morning or will they still do it in the afternoon trying to trick you into forgetting that you've already fed them that day?

So they will not see you as clearly through the air as underwater, but they'll definitely be –

seeing you and they've almost certainly remembered your presence.