Over dosing with Excel to kill algae

I battled algae for almost a year and decided to go the Excel route myself. I followed the instructions religiously, both at water change time and on a daily basis. It took a few months to get it cleared up but I've had no problems since, and continue with the Excel regime. I"ve had no ill effects on my shrimp, nerite snails, tetras or betta.

Sounds like you may be in a bit of a hurry, so I can't comment on "over dosing" and what impact it will have. If you want a quick fix and willing to do the work, you could also try H2O2 (regular hydrogen peroxide from a drug store). Move your livestock, drain the tank and then spray it all over the substrate and let it sit for ten minutes. Put a few inches of water back in and vacuum it out again to ensure you've removed/diluted the H2O2 sufficiently, then refill the tank. H2O2 is an oxidizer and will definitely kill the algae. It is very potent however. I occasionally use it underwater if a particular plant gets a little too much algae on it; turn off the filter and let the water calm then use a spray bottle underwater up close and give it a couple of blasts to the leaves up close. Too much in too little water can kill your livestock so be very careful. I made the mistake of spraying exposed plants during a 50% water change and my betta died within an hour from the concentration...lesson learned.