I had one before I went to England (came back and my entire fish stock died - my kids forgot to check on the fish) and I fed mine a couple of different things.
1. get an algae clip ($6.00) and green algae ($5.99)
2. Buy Frozen Formula one/Two 10.00 ea.
3. Buy Formula One Flake ( $6.00 for a lot) this happens to be all of my animals' favorites. they will turn down Frozen for this stuff every time.
4. Frozen Brine Shrimp $10.00
Feed the Flake twice daily (with a piece of fresh algae every other day.
Feed the Frozen twice a week rotating which one as you see fit.
The frozen should last a while using this method.