in a 5 to 7 gallon tank you can have 1 clown fish. nothing else i wouldnt even advise putting a shrimp in there but that IMO, its really hard to keep algae down because he probably had so much waste in the tank. daily water changes are probably irritating..
a 5 to 7 gallon is not gonna be the best choice for someone just starting but you seem like your researching so i hope it all goes okay for you! no bio wheel.. and get a better heater then a hydor mini heater.
i like harlequin shrimp but i dont want to have to keep starfish around to feed it because that can get pretty pricey