Soil under Sand Substrate

it depends on your setup & how your plant are doing.

Inch and a half layer of sand with no substrate heating, wouldn't the roots be cutoff from fertilizers in the water column regardless?

what I mean is your lighting setup, CO2?
and what are your NO3, PO4 readings? And how are your plants doing? Growing, dying, and what plants are they?

We can't really comment on anything without more info.

What you have sounds like a natural planted tank setup.
They don't usually add fert and have low lights.

My apologies, let me simplify my original post... If I use soil under an inch and a half or so layer of sand, would rooted plants be able to make an efficient use of liquid fertilizers.

yes, rooted plants can use nutrients in the water column through their leaves.

Yes, plant does eat quite well fron their leaves, and this also happens the same to most emmersed plants (the trick is to wait for them to open stomatas).

In fact, Tropica has done an experiment which according to them, giving water collumn ferts would boost plant growth even more, especially to those foreground plants which roots are short and unable to effectively collect nutrients from the base fert/soil below (they use traditional gravel method).

makes me wonder why people spend so much money on eco-complete

Rex mentioned in a another post that even Swords (which have I always heard require root tabs - being root feeders) can do fine with just water column dosing. That doesn't completely surprise me considering the size of their leaves, although I had never heard that before.

Tom Barr talks about cutting all the roots off of sword plants and having them grow like gang busters.

I also seem to recall Tom posting that most all aquatic plants will take up nutrients through the leaves before taking them up through the roots. Something about how less energy is expended taking the nutrients up through the leaves.

Of course I'm probably 100% wrong and Tom will come in an humiliate me in a very public fashion.

Very interesting.

I am always one to use what is available to me in the local waters for my tanks, and using soil under a medium sized layer of sand has always worked well for me.

I'm assuming you're talking about soil from the flower bed or the like? Or actually bags of topsoil from a garden store?

i used to have some red ozelot swords. they were planted in straight large-grain sand, no root ferts whatsoever. i dosed liquid ferts and they grew quite nicely. under 40 watts in a 20 long tank, they were about the size of my spread hand in diameter and bright red with green veins.

i never use specialized plant substrate, and i never put suppliments in the substrate. in my most recent planted tanks, i have been using uncented, non-clumping clay cat litter on the bottom, and sand on top, and my plants are growing great with just DIY CO2 and water column dosing (EI with dry ferts)