Habitat - Indoor :: Some advice about substrate?

[Wafelefaw]

So, I'm currently setting up a new aquarium for my two turtles. It's a 52 gallon tank and there's A LOT of DIY going on I'm trying all I'm able to do to make it not only comfortable for my babies, but also visually appealing. Now, that the tank is almost done I'm stuck with the problem of choosing substrate correctly. The thing is - I'm not from the US, and our turtle-themed communities really differ in the ways we treat our pets. Not in a bad way, just confusing. So here's options I considered and their pros and cons with the vision of turtle owners from my country.

River pebbles:
+ can be found in the wild (FREE)
+ turtle can't eat it
- a big no for me, don't like the appearence

Crushed coral:
+ turtles can eat it i guess??? from some sources but i'm not sure
- uncertanity on the subject from the info i found

Sand:
+ comes in a lot of colors
+ visually appealing
- can cause blockage in the guts??
- will wear off (? i don't know if it's the right word for it) the pump in the filter

Pebbles from pet store:
+ comes in many colours
+ turtle can't eat it
- since i need stones to be bigger than at least 2cm (~0,7in) it's very problematic to find right amount
- really pricey

Proppant:
+ looks cool
- i've seen this option only once, so can't be sure about safety

So, what are your thoughts? In our community the most frequent point in substrate related discussion is that turtle will eat it and it will cause a blockage, so the best option is to add a couple big stones and leave the floor empty. I really want to hear a second opinion, because it's a very serious matter for me.

[steve]

You're doing good research! You will not want anything that is artificially colored, as that would leach into the water. River rock (pebbles) do come in assorted brown/white/black colors but yes, you do not want too many in a tank. Pool filter sand is pretty popular as a substrate, most turtles will leave it alone. Any sort of fine substrate will require more regular maintenance. If you want to add some color to the tank, and you have a glass aquarium, you can add pictures or printouts behind and under the glass to make in more visually interesting.

Looking up Proppant, it is not something I'm interested in keeping near my turtles.