No problem. Yes, definately, if you were using a Ph buffer that will make your phosphates skyrocket.
One of the hardest things to get down, is how much to feed your fish. I've learned that you can't keep dumping food in the tank for those that "seem" to not be getting any. The hungrier they get, the more aggressive they will get. If they don't "seem" to get any food one day, don't worry about it; it's ok to feed your fish once every other day - keep this in mind and you'll see that they do get enough food. I feed 3 small portions everyday of a different kind of food each time - dry (flake/pellet), frozen, de-hydrated, as well as fresh vegatables when I feel like it. I know that there is enough food and nobody will go hungry. Sometimes, if I feel like I put too much in...that's it for the rest of the day. I don't care how hungry they look.
Here's a list of relatively low light plants that I've been working on:
Hygrophila
Water Sprite
Water difformis (Hygrophila difformis)
floating hornwort
Java Fern (Microsorum pteropus)
Java Moss
Cabomba (Cabomba caroliniana)
Moneywort (Bacopa Monnieri)
Anacharis (Egeria densa)
Dwarf Anubias (Anubias Nana)
Red:
Alternanthera reineckii - probably the best red plant for beginers
Ludwigia
Hygrophilia difformus or Hygrophilia tropica sunset
Echinodorus (sword plants) - a nice red sword can make a spectacular center piece
Cryptocoryne wendtii
Pearl Weed aka Pearl Grass or Hemianthus micranthemoides
I wouldn't focus on Co2 until you get more light. It's really uncecssary at anything below 2wpg. Actually, you can have a very nice tank of plants with 2wpg and no Co2 at all, however you will have better results. All of the complete Co2 systems I've seen are too much money.
www.drsfosterssmith.com has a complete system. When you say you don't want DIY, do you mean that you don't want to buy seperate parts and put it together? This is by far the best way to go. You get better parts and it's cheaper than the all-in-one packages. I picked up a Milwaukee regulator with 2 gauges, bubble counter, needle valve, and solonoid for $80.00 at
www.aquaticplants.com. It's a pretty nice and reliable all-in-one unit. Then all you need is a 10lb. (I wouldn't recommend anything smaller for a 140g) Co2 tank that you can get at any welding supply (you can buy your own ($100.00) or put down a deposit and rent ($50.00) ...similar to a keg of beer or propane), a Co2 reactor that you can buy ($60.00) or DIY (lots of plans for these on the net), Co2 line, check valve, and timer. You run the Co2 during lights on and turn it off at night (plants don't photosynth. at night). And that's it.
Yes you can run aeration with Excel...it's liquid carbon, not carbon dioxide.
How deep is your tank by the way. The 2wpg guide is for NO (normal output) flourescents at a depth of about 20". If you go with PC you can figure you have a little more wpg, but if you're deeper than 20" you can figure you have less wpg.
Sounds like your substrate is good.