Eco + underlayer of ADA?

I realize this undermines the nice look of the ADA substrates, but since it is relatively expensive, is it possible to simply use it as the lower layer? Especially if I use the powdered form? The other question is that this is a downgrade--I already have a few fish. I know ADA tends to cause some initial problems, but would the layering help to circumvent that to any degree? If not, I'll just go with 100% Eco and use plant spikes and the like.