Here is an update. I have replaced the bacopa with Mayaca Fluviatilis (which has grown like crazy), removed the wisteria and replaced some of the dwarf sag with pelia. The guppy grass is gone as well.
I got the rocks from ebay, just search for lava rocks. Interestingly, I have these rocks in 2 different tanks, and the plants are doing a lot better in these 2. The nitrates are really low too with the rocks, in the shrimps tank they are actually 0. I suspect that lava rock has nitrates-removing properties.
Nice, I really love how this tank is developing, the moss wall has really grown in, and I like what you've done with the rest of the tank in general, awesome job! Replacing the bacopa was an excellent decision; the mayaca looks so much better! And even though I have some dwarf sag myself, (got it as part of a plant package a long time ago), I never really understood its popularity. It just seems drab and boring to me... though I guess every salad needs its lettuce right? I think the pellia was an excellent decision. It adds a really, really nice touch, though I've always been partial to pellia and its fellow liverworts. The pellia just adds a lot of "feel" to the tank imo, it really helps mix up the texture and color of the tank, without detracting from the overall color scheme. And the visual contrast between the pellia and lava rock is great! It also helps add some more sense of visual depth if you know what I mean, makes it look more "3D" lol.
As far as the lava rocks and their nitrate removing properties you mentioned, I'd bet this has something to do with the fact that it is a highly porous rock, essentially creating a gigantic growing bed for BB. As far as purchasing lava rock, I've actually dwelled on purchasing lava rock or driftwood from eBay for awhile now, I've done it in the past with small pieces of manzanita or malaysian driftwood, but right now I'm on a tight budget and I don't want to pay outrageous shipping costs. But then again, I might end up paying less overall, or getting more rocks/$ overall, which does not help my indecision and reluctance to shell out the money. I'm thinking of hitting up some stores in the city tomorrow and scouting. All I know is I want some, and if I walk into an aquarium store with money, well.... it's hard for me to leave with it