Offered to take an unwanted rainbow shark from a family member's hands. All I have is a 20 gallon long tank. I've read rainbows need a large (55+?) tank due to aggression with tank mates. I don't plan on having other fish. I think a rainbow would look nice on it's own in a planted aquarium. Will a 20 gallon long suffice if the rainbow shark has it all to himself? Or are tank mates required for stimulation or other reasons? If it is healthy or necessary for the shark to have tank mates, would a handful of white mountain minnows be okay to share the tank? I'm also worried about lighting. Will LEDs bother the shark? Are they sufficient for plants? What are good plants for the shark? I like the look of water wisteria. ...I have zero experience.