I have my Venus Flytraps planted in Perlite and Sphagnum Peat Moss. I water them with distilled water, which is in a tray that the plants sit in. I keep them all in a ten-gallon fishtank with cling wrap over the top, so it's good and humid inside. The plants get plenty of sun, and I occasionally take the cling wrap off so they might catch something. I originally had four plants, but I let two flower and they died. Lately, I've noticed a strange green substance on the Perlite. I don't know if it's harmful to the plants, but I'd like to know before it gets bad...what should I do?
The environment is probably more humid than required and I doubt the cling-wrap is necessary. It will be encouraging the growth of algae which is almost certainly what you've got. The surface of all pots will turn green in time and is not normally anything to worry about.
Yeah, I don't grow my Venus flytrap in a humid environment at all, to be frank I think terrariums and similar conditions are wasted on them, they don't need that kind of humidity. The humidity in my area often drops below 40% and they don't even react to it. They are one of if not the easiest CP to grow, so there isn't any reason to try to adjust the humidity unless you live in a super arid area. A picture of the plant and its container would be useful too.
Nothing compares to the joy of growing a plant from seed and watch it prosper.
Dionaea muscipula are one of the last plants you'd want to have in a terrarium. I live in CO, where temps soar to well over 100 F during summer on occasion and average humidity MIGHT reach 20% on a given day. Often it's less than 15%, and my flytraps do just fine. Likely, the algae or slime mold won't hurt the plants, but it is unsightly and you can probably scrape it off, and then put on a fresh layer of top soil. Also, as other people said, the flowering probably wasn't what killed the plants, unless you hadn't had them that long and they were etiolated or ill in some other way to start. Mine also flower every year and have little trouble just continuing to grow.