When starting a new tank I like aggressive growers like Hygrophila polysperma or Heteranthera zosterifolia (stargrass). For low growers, my absolute favorite is Glossostigma elatinoide. Staurogyne repens is excellent as well, but it's a bit more maintenance to keep it low. Hydrocotyle sp 'Japan' is a great midground plant. If you don't have any luck locating a source for plants, send me a PM, I might be able to help you out.