springtail shenanigans

hi all, I’m having some weird things happen in my 25g paludarium. Invert-wise, it’s stocked with cubaris marino glacier isopods and basic white springtails in addition to plants and my Cuban tree frog. all is well, the system is seemingly thriving, except for the fact my springtails seem to exclusively live on the water. they’re not drowning, they can walk on the surface tension and I can see them wiggling around, but I can’t seem to stop them from just living on the water. has this happened to anyone else? is there a reason they’re stuck in the water? I’ve put pieces of wood and stone sticking out so they’d have a place to go to, but they still choose the water. does anyone have any idea why this is happening?