Is gravel is a good substrate for cory? Or is it definitely a no-go?

Definitely a no - the gravel will damage their barbels.

Agreed, sand for Cories

Thanks for fast reply!!!

Can you suggest some bottom-dwellers that go well with gravel? The only I think of is flying fox

How big is the tank (litres and width, length)? What are the pH and hardness? What other fish are (or will be) in this tank?

It's 120cm long, 40cm wide and 50cm high, that's 240l but with the decors and substrate, it's around 200l provided by the substrate is very thick.

It's the tank I mentioned before, pH should be around 6.8 and I'm planning to keep some tetras too

Mmm, can't really think of anything that would be OK with standard gravel. Most bottom dwellers do better on sand for obvious reasons. If you can get some small, very rounded gravel with no sharp edges and mix it with sand some of the smaller plecs will be OK, but that's about it for soft water.

It's the smallest gravel available in my area, it's about the size of an neon's eye. And it's round too but I can't guarantee 100% no sharp edge.

The thing I'm afraid is that plec will dig too much and un-root the plants.

What about mid-dweller and top? Can I keep a pair of Apisto or gourami? I mean just tetras alone would be boring

If it's that tiny and smooth Cories would be OK (though sand is really preferable). They may dig too though.

Apistos would be OK, but once again would do better on sand - they are bottom dwelling. Gouramis should be OK too.

I used to have a yellow/orange catfish and they were fine with the gravel, also the flying fox were fine, I don't know if the cories will.

Can I have both apisto and gourami? I've never had apisto before so I'm still considering this. Do they have any special requirements?