You want a decent amount of water retention for VFTs... I don't really grow that many and so my experience is limited, but you might be able to get a net-pot and put some rockwool in that, and have the VFT grow in the rockwool, with the pot under the gravel and out of sight. Generally almost anything can grow in rockwool if given the right micronutrients. Why do you want to avoid using peat?

The whole bog is going to be pea gravel and I don't want to make exceptions. It's really more of a "veggie filter" for the pond. I can always find somewhere else to put them if they won't work there.

Thanks - Jenion

I would probably just put them somewhere else then, because pea gravel would be too loose of a substrate I would think.

From what I have seen VFT will simply not grow well, if at all, in anything that does not contain sphagnum peat moss. The acidity and water retention in that moss is just the environment the VFT adapted to and it is a very specific dead end evolution that plant has gone through. The plants that have been grown in pure neutral substances, like perlite with no moss, were puny, weak, and half-dead looking.

Make it a 50/50 mix of pea gravel and peat moss and you'll probably be o.k. Straight pea gravel won't work. Plus you HAVE to treat it like a bog and keep it moist with NO TAP WATER.