I assume you want floating plants for your goldfish to eat?
Just set up some large plastic tubs outside in the sun or under part shade. If it gets really hot in summer then have them under shade cloth during the middle of the day. Fill them with tap water (you only need 6-12 inches of water) and add some garden fertiliser (1 level tablespoon of granular fertiliser per 20 litres/ 5 gallons of water). Stir it up and add some plants. The water will go green and soupy but the plants will also grow.
Any floating plants will grow outdoors, including Water Sprite, Duckeed, Azolla, Water Lettuce, Water Hyacinth, Salvinia.
You can grow Water Sprite and Duckweed in the small tank under LEDs. If there's no fish or shrimp in the tank, add garden fertiliser at the same dose rate mentioned above.
You can either drain the tank/ plastic containers every week or two and refill them with clean water and more fertiliser, or just add a half dose of fertiliser every 2 weeks. If the plants are growing really well, then you can add a half dose of fertiliser each week.
If you don't rinse the containers out and refill them each week, you will probably get lots of insect larvae in the water (mozzies and bloodworms) and these can be fed to the fish. You should watch for dragonflies, if they are hanging around the containers, they might lay eggs and you might get dragonfly larvae in the containers. They will eat small fish so check plants before adding to a tank with small fish or shrimp in.