I would venture a guess that this would be a great experimental 10 gallon tank substrate. However, with the way all three of those materials function biologically/chemically, the real interesting stuff wouldn't happen until about month 10 or 12. As others have mentioned, the vermiculite will float. I suggest you soak it for awhile, and then smush it all together (if you don't want to get your hands dirty, you could try a bucket and a potato masher I guess, but who doesn't want to get their hands dirty?).
You want to get the vermiculite to absorb as much water before you start planting as possible, or you'll have bits of it floating in the water column every time you pull out a plant. This might, really, defeat the purpose of vermiculite in general, however. It has a very high cation exchange rate as its essentially a clay but I don't know how that changes when its been all mushed up. Probably not much, I just assume that the CEC is only measured for terrestrial planting.
ANYWAYS, give it a shot. I had a tank with mostly playground sand, vermiculite and peat moss, and it did fairly for the first year and started to take off towards the end of the second year. Then my fish got sick and due to a number of other reasons I had to tear it down. Were I to do it all over again I'm sure I'd fair better, so it wasn't necessarily the substrate's fault. I'd be interested to see your results with it. If I had the space I'd try it myself.
You want to get the vermiculite to absorb as much water before you start planting as possible, or you'll have bits of it floating in the water column every time you pull out a plant. This might, really, defeat the purpose of vermiculite in general, however. It has a very high cation exchange rate as its essentially a clay but I don't know how that changes when its been all mushed up. Probably not much, I just assume that the CEC is only measured for terrestrial planting.
ANYWAYS, give it a shot. I had a tank with mostly playground sand, vermiculite and peat moss, and it did fairly for the first year and started to take off towards the end of the second year. Then my fish got sick and due to a number of other reasons I had to tear it down. Were I to do it all over again I'm sure I'd fair better, so it wasn't necessarily the substrate's fault. I'd be interested to see your results with it. If I had the space I'd try it myself.
