Do fish react to having people around?

So for the last two months, my fish have been at my old flat, while I have been at my new one. I was going in a few times a week to feed them and do water changes, but wasn't around too often

I was getting really worried about my snakehead's behavior - he was sitting on top of the filter, refusing food and was just not doing much.

I moved them over to my new flash yesterday, and already the changes are startling - he's pretty much back to normal behavior - is eating like a pig, cruising round the tank, hiding in different areas and just generally being himself.

Any ideas? Given the only difference is I've been around constantly. Anyone else experienced this?

Plus, does black sand help colours come out more?

Meant to add, he had lost his colors a lot the last few weeks, but since yesterday, they are really starting to come up - showing he's less stressed

Ok I'm glad other people have noticed it before and that I'm not going mad and the water was pretty good anyway (nitrates stick at about 5) but guess a 100% change will have helped it

He really is eating like a pig again, which is good as he was practically starving himself.

Despite the fact I do 40% weekly and the parameters were perfect?