Slade;

*Live* algae plugs DE filters rapidly; *dead* algae does so MUCH more slowly. So, kill the algae.

As Watermom says, it will take lots of bleach. I'm guessing you are about 15,000 gallons (27' x 3.5' water depth), so each gallon of bleach will add about 4 ppm of chlorine. For a swamp, you probably need to think in 16 ppm / 4 gallon doses.

Do this:
+ Go to Walmart and purchase a cheap OTO/phenol red test kit and about 24 gallons of bleach. You can also get a few boxes of borax and some stabilizer if you can find that there.
+ Make SURE (really, really sure!!) that if you have a feeder, tab feeder, Nature 2 or other gizmo the tabs, filler, cartridge, etc is REMOVED.
+ Run the pump / filter 24/7
+ Add your bleach THROUGH the skimmer. This will kill the algae on the DE, first before the bleach reaches the pool and will help relieve the rapid plugging of the DE.
+ Meanwhile, keep scooping and vacuuming.
+ Test the pool 1 hour after each bleach addition; repeat the dose EVERY TIME the chlorine goes below 3 ppm.
+ If the chlorine is still high, but the OTO does not turn ORANGE, and the filter is stopping up, add *one* gallon via the skimmer, to see if that will relieve the high pressure. If not, wait 15 minutes and then clean the filter again.

With a DE filter, you should be able to clean your pool up pretty quickly (a day, maybe?) if you can keep working on it.

Ben