oopsmysocks

So I've tried to keep floating plants in my covered betta tanks (on two continents!) and always after explosive growth the populations collapse. Makes me feel like an idiot because, well, it's freaking duckweed/water lettuce.

This time I pulled some duckweed and water lettuce aside and put them in a half filled 1 gallon bowl in a window sill. They seemed to be doing well for a while, but for the last few days the water lettuce has begun turning yellow, with leaves eventually becoming transparent.

There's little else in the bowl, except for some Java moss and I add fish food - I used to every other day and have gotten down to once a week. There was a bit of algae in the bowl but after some thorough clean up, it seems like that's gone.

Anyway, it looks like the water lettuce needs iron - is that correct? If so, is there an easy way for me to add some to the bowl? Since there are no fish or inverts in the bowl, I've got a free hand and I'd like to figure out for the next time I add floating plants to an aquarium.

Thanks!!

EDIT: I've got some organic potting soil on hand if that would help, but it's the Scott's Organic stuff which likely doesn't have iron I think.
May be it's Potassium instead? In either case is there anything I can add that will make it better? Should I get a bottle of Excel? Could I just add soil from outside?

Sophie and Mom

Hmmmm....I can't keep mine dead. Is it an actual planted environment with dirt and the usual planted tank stuff? It may need the nutrients that leech out of the soil and into the water column. They seem to do especially well in a tank that's cycling, so maybe actually make your bowl a planted bowl and throw them back in to see how they do.