Photo album of my tadpole setup: http://imgur.com/gallery/LuD7i

I allowed my setup to cycle for about a month prior to adding anything - I used a filter from a coworker's 50 gallon goldfish tank to inoculate it, confirmed that all the water parameters were correct (and then went to the local fish store for them to confirm). I got 9 grey tree frog tadpoles from someone's above ground pool on Wednesday. I mixed some of my water in with the water they came in and let them acclimate for a few hours, then put them in this setup (which at the time had a lot more algae and no airstone). Thursday everything was fine, Friday three died and I panicked, thinking that maybe they weren't getting enough air with just the filter so I added the airstone, and today (Saturday) one more has died. they act normal and healthy until they die. I've been trying to get them to take boiled lettuce or zoo med tadpole and aquatic frog food, but all they seem interested in is the algae on the sides of the tank.

What could I possibly be doing wrong? I'm very close to just tearing down the whole tank and starting from with freshly treated tapwater, but I'm worried that if I do they won't eat (since so far all they've wanted is the algae)