I almost forgot about the puffers! The arrowheads will destroy fish in that tank,but don't move around too much,for something crazy and super active, try the bronze or avocado puffer too! A. modestus, they are sweet !!! Puffers are a legitimate contender in a 35 gallon! Also look into a rainbow wolffish they are similar in behavior to the arrowhead puffers, kill ,rest,kill,rest......... and should be able to fit in your tank.