This plant can be a saviour. It secretes antibiotic substances which can help to prevent cyanobacteria (the blue-green algae). This fact alone makes it a must have plant.
The negatives of including Egeria Densa are that (1) It will grow extremely long regardless of tank dimensions (like the onion plant), then it can hog the tank's light for other plants as it spreads itself across the surface; (2) It can become a collection point for fish faeces and other undesirable deposits over time, this can discolour the plant if not removed. Otherwise it is a good fast growing beautiful plant.
I am new to aquariums and I just got these because they were US$1.50 at the store for a bunch. Unfortunately, they had snails, but nothing a quick bleach dip couldn't take care of. I let them float at the top of my small Eclipse 25 L and they grew like crazy. Not to mention that my goldfish loved them. I transplanted the clippings to my 115 L and they are doing great! No CO2, no fertilizer. I just wish they would stay in the gravel better...they seem to float off every once in awhile.
Great plant. Tends to grow thin and strappy if not given sufficient light. Grows in almost any condition, and provides good cover for fry. Delicious to fish such as goldfish, and to humans. I tried some!
I didn't have a fluorescent light on my tank for about 4 months and this amazing plant was able to grow with a normal 60 Watts incandescent bulb. I love it, and it became even better when I used the adequate lighting, so I guess it can handle not so bright light as well.
This plant is a favorite of herbivorous fish that just love to nibble at the green leaves, especially with my goldfish that quickly decided it was an ideal breakfast bar. Make sure to secure it into the substrate because it tends to escape and float around.