I realllyy wanted black sand for my new betta tanks but the pet store employees convinced me sand wasn't good for bettas and they needed gravel...I got the gravel and added it to the tank (not a fan of the gravel look) but I looked it up later and most says sand is fine. Thankfully I didn't take any of their other advice which was more important (they said no filters and the main girl I talked to said bettas can only be in bowls or very small tanks-that the 10 gallon I got was "too big for a betta") Anyway I wanted to pick up some black diamond sand from tractor supply because it looks nice and is really cheap and I read a lot of good things about it for aquarium use. They come in 50lb bags so I wanted to use some of it for my 75 gallon tank which I plan to have some bristlenose plecos in. Should I use fine or medium grit sand for the plecos? I don't want to scratch them up.