actually you've got very poor light, something like 85% of the electricity used by incandesents is put out as heat(i think it's actually higher) and the rest is usually off spectrum for plants. i once did an experiement and had trouble growing algae under a 15w incan. upgrade to 2x10w or 2x13w CF daylights(availible in 5k, 55k, 65k and i believe 67k, i prefer the higher k bulbs) for about 6bucks and then you'd have decent lighting.
pinkplaty, i don't think a single plant in that tank is a true aquatic plant, that could easily be why you've got ammonia. there are dying plants and they aren't consuming any nitrogen compounds from the water. if you light the way the plants look then consider getting swords or java ferns to replace the tall ones, crypts to replace the midground plants and pygmy chain swords to replace the mondo grass in the from.