The only plants that mine ever tried to eat were red ones with fairly delicate leaves, so I try to avoid including those. However, do you give your plecs vegetable matter to eat, such as cucumber, courgette, squash? Since I started putting a chunk in each day they stopped eating the plants. The favourites are courgette, butternut squash and sweet potato - the cucumber was pretty much rejected! I weight these down with a small piece of lead strip of the type used to bunch together plants, then remove any uneaten vegetable matter the next morning. I also give the plecs Hikari algae wafer, which they seem to like. Not sure what plecs you have but I have two bristlenoses and a common plec.