Oh I believed you when you said your plants hadn't caught any. That is a moranensis type plant, possibly a hybrid and will catch gnats. It could use a lot more light. The leaves are quite etiolated and this is probably why the gnats are not sticking. For reference, I grow mine about 12-14"" under 6 bulb HO T5 fixture. They don't need this much light, but it gives them nice colors.
the leaves are slimy/sticky and do well enough in holding on to dead bloodworms.......just not sticky enough for gnats. I even tried a mealybug and it crawled away !
The plants are in a South Facing Window and get quite a bit of shaded sunlight, and even some direct sun. I started with one and now have 3, so it does produce "keikis" in these conditions.
None of my plants are under artificial lights.