I am in the process of cycling my tank and will be getting my oscars soon. as of now my substrate is small gravel and it looks great but i feel like it might hide waste in it because the pebbles are just barely too big to get sucked all the way up in my vacuum. my thought is to get some sand substrate and do a mix. not a whole lot of sand, but just enough to fill in the cracks and negative spaces between the gravel....is this a bad idea?

I do not know about mixing the 2 substrates.
But i use 4 different sizes of gravel, very small to medium sized.
The purpose is to hide the waste, until i do my gravelvacuuming.
That will still have to be done weekly in my tank...
When i gravel vac all the dirt will come out and the tiny gravel will be on top of the other gravel, so it's very easy to see which parts are cleaned allready and which are not...

mixing gravel with sand ...I tried this and it made a hell of a mess

The sand will go down between the gravel and will almost create a cement and your substrate will become very compact and hard and to top it off it doesn't look to nice either and will become more prone to pockets of gas building up etc etc id stick with one or the other mate ..honestly

Im with staffie, stick with one type

ok, ill stick with the gravel then....thanks staffie

no problems any time