Since I'm a local, I know what it is like to deal with our liquid ROCK water. I'm thinking that what you need right now is a reset. Clean the tank out nice and good, change a good percentage of water, and start from the beginning. Get a good fert schedule going (not saying yours isn't good, but it may be helpful to double check that you're not missing anything), and put in a LOT of plants. There is no quick and easy solution to algae troubles, and sometimes by "trying too hard" we end up making it worse. Be patient.
First and formost, buy an appliance timer (<$10) at Walmart and plug your lights into it. Set the timer for 8 hours a day until you get that algae in check and then bump it up to 10-12. Replace your bulbs when you can - get a good full spectrum light (you don't necessarily have to splurge on those expensive plant lights - I've grown plants just fine on good old full spectrum standard flourescents, but I prefer power compacts). If you can afford the upgrade, www.ahsupply.com
has great retro-fit kits for PC lights.
The 125 gallon is a bit big for DIY CO2 - though even a little might help. If you're close (I live on the N. side of Indy) I'd be more than happy to make you a DIY reactor, get it bubbling, and show you how to change it. A good alternative to compressed CO2 is Seachem's Flourish Excel. If you do order it online, try for the BIG jugs of it, much more economical (http://www.bigalsonline.com/catalog/...egory_id=3141)
I'd also be more than happy to hook you up with a handful of clippings to get you started. Again, if you're close, you may look into coming to the CCAC where there's always lots of clippings available. We're also having a big public auction at the end of April which will be loaded with good stuff. Packing the tank as full as you can with plants tends to really help get rid of algae because they compete for the same nutrients.
Where is Camby, IN? I live in on the north side of Indy.