You have an acidic pH, so this is preferable for aquatic plants. You don't need to worry about the chemistry of the tap water. Fish and plants will adjust. Start with hardy plants. Anubias, Amazon swords and Java fern for the bottom. Some good floating plants that don't require planting in the substrate are: Pennywort, Anacharis (Elodea Densa) and Hornwort. Just maintain clean water conditions. Add some hardy fish and feed them a balanced diet. The fish will provide the plant nutrients.
"Fear not my child, just change the tank water."