Any recommendations for fast growing South American plants?
I have the cabomba written down.
Cabomba is not an easy plant. It is fast growing, which means brighter light and more nutrients. Most but not all of the stem plants are similar.
The easiest fast-growing plants (thinking of the "silent" cycle aspect) are floating, like Water Sprite, Water Lettuce, Frogbit; Brazilian Pennywort is one stem plant that grows very well if left floating.
Other easy SA plants that will not be so fussy about light is the chain sword,
Helanthium tenellum. [This plant may still be seen as
Echinodorus tenellus.] The true sword plants in
Echinodorus are fairly easy too, but many get too large for a 20g long. But having said that, sometimes they tend to stay relatively small. I have had this plant grow leaves 30 cm and longer, while some of the adventitious plants produced along the inflorescences remain 10-15 cm.
If I'm not adding ammonia to a planted tank, what do I do? How does the cycling work? I can't find anything on the net that goes in depth about using plants for cycling.
I'll just add a bit to what seangee mentioned. I only use this method, and for over 20 years. You need fast-growing plants, and floating are the best; you often see floating plants termed "ammonia sinks" because of their capacity for taking up ammonia/ammonium.
Aquatic plants obviously need nitrogen, and they prefer it as ammonium. Nitrate is only taken up when ammonia/ammonium becomes insufficient in balance with light and other nutrients, because the plants have to spend energy converting the nitrate back into ammonium. With floating plants and other plants growing, you can add fish with no issues, though initially I suggest you start slowly.
The nitrifying bacteria will still appear and establish, but with the plants taking up most of the ammonia, nitrite is very minimal, and nitrate the same. Test kits won't be able to detect ammonia or nitrite during this process.
