Seeing the above pic got me thinking of the magnetic bulldog type clips you get for your fridge to hold heavy paperwork on the fridge. If you had an old one that had lost its magnet it would work just as well I think.
Wow so many alternative uses for everyday household bits and pieces, it could probably become a topic in its own right.
My BN's didn't immediately take to eating zucchini but now you can't keep them off it. I guess some foods they have to aquire a taste for.
And I just remembered in relation to your question about giving your pleco fruit, I once gave my BN's the rind ( the skin with the white and some red still attached) of a watermelon which they seemed to really enjoy. Didn't cause any deaths and the water stayed fine, I am guessing they would also have a go at rock melon as well. Although I'm really not sure if it was a brillient idea to go experimenting with the different fruits, all I can say I didn't experience any problems, and the BN's that ate the watermelon are all huge and are going on for around 6yrs of age now and regualrly breeding.