It's funny that you say that plain looks more natural - if you go to many rivers or lakes that are heavily vegetated (aka, have lots of plants), you'll find most in a dark, muddy substrate. Sand is closely related to glass - it's just silica. It has NO nutrients for plants, by itself. Over time it can accumulate bacteria that'll help make the fish waste more accessible to plants, but ultimately, any substrate can do that.
The pet store guy may have been trying to push Eco-complete on you. Does that sound familiar? It would have been a blackish substrate with varying sizes, from small sand sized particles to small gravel pieces. It also has water already in it, with various microorganisms, namely bacteria, already seeded. Though this stuff is nutrient rich and seeded with bacteria, you'll find that ANY substrate that's kept well will eventually develop those same bacteria... just a waiting game.
The nutrient richness from eco-complete or flourite is high indeed, but many other people succeed with just root tabs... or by getting mineralized soil. I think most hardcore plant people would argue that mineralized soil is the best - it's incredibly nutrient rich and will last forever, really. My ecocomplete is now mostly devoid of nutrients after 7+ years, but others have used MS for twenty with no problems.
That being said, MS and other soils are all going to be darker colored, which is indicative of more organic matter. You can put sand on top and be just fine with that, if you like the color of the sand more.
The pet store guy may have been trying to push Eco-complete on you. Does that sound familiar? It would have been a blackish substrate with varying sizes, from small sand sized particles to small gravel pieces. It also has water already in it, with various microorganisms, namely bacteria, already seeded. Though this stuff is nutrient rich and seeded with bacteria, you'll find that ANY substrate that's kept well will eventually develop those same bacteria... just a waiting game.
The nutrient richness from eco-complete or flourite is high indeed, but many other people succeed with just root tabs... or by getting mineralized soil. I think most hardcore plant people would argue that mineralized soil is the best - it's incredibly nutrient rich and will last forever, really. My ecocomplete is now mostly devoid of nutrients after 7+ years, but others have used MS for twenty with no problems.
That being said, MS and other soils are all going to be darker colored, which is indicative of more organic matter. You can put sand on top and be just fine with that, if you like the color of the sand more.