I have found some plastic fittings I would like to work with in constructing a UGJ system. They are great in almost every respect, low profile and totaly ajustable inside a set up tank. Their down side? They are red and yellow. I have read on Frank Muellers web site about his use of RIT dyes to dye his PVC but this plastic is so hard it is almost like glass. I'm pretty sure it won't take dye. A black permanent marker would be a very easy soulution as I have black colorquartz for substrate. Anyone know anything about potential toxicity of that sort of ink. Seems like I've seen aquarium decorations at LFS priced with them. Thoughts? Thanks.