Substrate question for my wife's 5 gallon planted guppy tank
So my wife really liked two guppy/endler hybrids (still unsure on these) at exotic reef, and I told her she should start her own tank with one of the tanks jeander gave me. (Thanks again!) and so we got her set up right away with a 5 gallon acrylic tank, we used water, plants and some extra sand from my 20g high and the sponge filter from my 20g to make it as Pre cycled as possible. Plants so far are just a pothos vine and another small vine from EntoCraig, water wisteria, and some duckweed; which are all floating right now because of the lack of soil.
Here is my question, right now there is only 1/2 an inch of sand, bc I couldn't spare anymore (I honestly need more in my 20g) but I was just wondering what would be a good cheap substrate for her 5 gallon. (Whatever extra there is I could use in my 20g)
She's not sure what plants she wants yet, but she wants the tank to be as low maintenance as possible, the 2 guppies will probably be all she has in there, maybe a beta some day, and whatever MTS were transferred from my sand. So whatever recommendations you guys can make would be great. Thanks!