I've been trying to sift through all of the info on this forum and I have to admit I'm a bit overwhelmed as I'm new to the planted tank thing. Any help you can offer would be so awesome... Here's my situation:
I'm setting up a little 5 gallon tank that I'm planning on planting but keeping very low tech. I only have 11 watts of CF lighting over it so it'll be low light, low tech though I will dose with the Flourish line of ferts (NPK, Iron, traces) and Excel (since I already have them for my other tank). The plants I'm planning on having are probably a couple of different anubias species, java fern, some mosses, plus maybe one or two swords or crpyts.

I'm trying to figure out what substrate to use. I like the look of the SMS and Aquasoil, but I'm wondering if it's practical since the plants I want aren't really root feeders (well, other than the crypts or swords and I can always supplement with root tabs if I use inert substrate). If it will help the plants grow better I'm more than willing to use the best substrate I can get. Will it make a difference if I use a plant substrate? I really want a dark substrate - if I don't go with a plant substrate any suggestions for an inert dark substrate that is fine-grained like that?

Any advice from all of you experienced plant gurus out there would be greatly greatly appreciated. Thanks so much in advance!!

The main reason that you want to use plant substrate for these plants is so their roots can take a good hold in the substrate. I've found that they dont attach themselves to the stone type substrate but readily do so with the clay based ones.
If you want a dark substrate SMS charcoal is going to be your best bet. And really look at it like this.
you can go to Petho and pick up a 15LB bag of gravel for 15 bucks. OR you can take your 15 bucks to Lesco and buy a 50 lb bag of SMS. for me thats an easy decision. Even in non planted tanks I use planted substrate. honestly it just looks better.

one or two swords? swords grow over 24 inches. I dont think you want a sword.

Yeah I know, I was thinking maybe micro swords for a sort of grassy effect to contrast with the mosses and the larger leafed anubias.

So then I guess I've decided to go with the planted substrate. Is there anywhere to get smaller amounts of SMS than the 50 pound bags? I'm doubting that I'll use even a third of it for my little 5 gallon tank (it's really a matter of not having anywhere to store whatever I don't use). In any case I'll have to find out if the Lesco store nearest me has any in stock...

Thanks again for all the help!

Sadly no. 50lb is the smallest they come in. (actually I think they are 40lb bags) Your best bet is to see if anyone else in your area might wanna go halves with you on it. I'd do it If I was in your area. we can't seem to get SMS over here in wa.