Seriously. I can't keep any aquarium plant, not even the mighty and feared
duckweed alive. I bought a quarter pound of it along with another floating
plant and its almost all gone now in three separate aquariums. Fish and snails
kill all my rooting or potted plants. I figured with duckweed, it would
reproduce faster than the fish would eat it. The fish are all fat and happy and
healthy so the water conditions cannot be that bad. I use aquarium plant
fertilizer solution have fair to good lighting and decent NO3, NO4 readings (I
use plastic embedded test strip sensors from SeaChem).

One tank contains 2 red eared slider and one Florida Peninsular Cooter
hatchling turtles, 5 large Goldfish and one Madagascar Sailfin Molly ( may
sound strange but its the only molly I have ever been able to keep alive, and
it's happy there ) as well as one large mystery snail and an algae eater.

The second tank contains a pictus catfish, 3 Lombardi cichlids, 3 angel fish, 2
blue acaras, 2 kissing gouramis, 4 tetras, and a tiny peacock eel, an algae
eater and three tyes of snail.

The third tank contains 6 half inch dwarf puffers, 5 red clawed crabs, 1 golden
fidler crab, 9 dwarf african frogs, varying numbers of ghost shrimp, 5 guppies,
2 green barbs, 2 tiger barbs, a american flag killiefish and one eastern newt
and varying madagascar icecream cone snails. This is the tank where plants have
lasted the longest and it has to rely on my computer work area light (a single
flourescent) for its lighting needs.

What can I try next to get plants to grow or remain alive in my tanks?