what types of food are good for fish besides flake food?

The pleco would appreciate it if there was a bit of wood in the aquarium. Drift wood that has been boiled for nearly a day is good, and you can buy some pre-boiled at most pet stores. Plecos gnaw on the wood and seem to derive some sustenance from it.
The pleco would love a sinking algae pellet, and you can experiment with slices of cucumber, carrots, cauliflower, lettuce, etc and see what types of foods it likes best. Remove the vegetables after a couple hours so that they do not rot and foul your water.

The female betta would really like some freeze dried blood worms, but you said that you don't like worms, so, you can try freeze dried brine shrimp and see if you're okay with those. She's a carnivore, so she needs a little bit of meat every now and then. Guppies also love dried brine shrimp and blood worms.

Personally, I own many different kinds of fish food and I feed my fish a variety of everything. I've got two kinds of freeze dried shrimp, blood worms, several kinds of flakes, sinking algae pellets, etc, etc. The fish like variety and seem to be healthier for it. :)
 
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