Changing To Sand

[Gurglar]

So i've decided to change my 3 foot tank to sand and am wondering if you guys think its a good idea to use a layer of my ADA soil underneathe the sand?

I do plan on having a planted tank (just simple no Co2 etc) and am wondering if its worth putting a layer in or just leave it as sand?

 

[soybean]

It will mix together eventually, especially if you have bottom feeders like corys moving it around. I have plant substrate underneath gravel and even that is mixing together in places. I regret putting it in - I'm sure it's doing my plants good but I wish I'd gone for all sand instead