I have the hammock, too. It will be safe and mostly useful to some fish as long as you take the wire out; that's what I did.
I have four of these leaf hammocks (one of them I have had for almost three years) and I have never seen the metal wire nor have they caused any of my babies any pain. It is the EXACT same one shown in the picture earlier in this thread too. So that is strange to hear.
Not an ornament as such, but I just wanted to warn anyone out there about placing Chinese Jade or Garnet in your tanks. I tried this once to add some colour to my tank, within 2 days my PH had skyrocketed (my water is normally slightly acidic but it went off the charts alkaline)! This was in a 5L tank, but I think these stones would do the same to bigger tanks.
My betta was fine by the way, luckily the tank was new and I was testing the water every 2 days!
Good materials for tanks are: quartz, glass (great for pops of color), sand, silk, ceramic for aquariums (but make sure the paint doesn't peel off and cause a decline in water quality), and, in my experience, soft plastic aquarium plants. That list is based on my knowledge of chemistry (I'm a science major)...none of those materials are reactive with stuff in water.
Personally, I'd steer clear of any non-glass items that are brightly colored -- they're most likely to peel away.
This is a good thread, however I have the pineapple mentioned on the first page and I've had it since last September without any issues. Now, last week I was pulling it out of the tank to clean it during a water change by the "plant" part and it literally just fell apart. I bought a new one on Amazon, and while browsing I realized there's a version made by Penn Plax and a version made by a different company that are almost identical. The other version has larger windows (so I guess, in theory, would be better for bettas). I bought that version to replace the now broken pineapple I have. I'm not sure who made the one I have at the moment anymore. From other things I read, if there's issue with the pineapple it's probably the Penn Plax one. Also, I have one of the betta hammocks as well since September and I clean it at every 100% water change and have never found anything wrong with it.
This is a great idea to have this list, I would have added this sooner if I knew it was here.
Paint peals off this betta log after a few weeks....
I took this picture when I noticed it and sure enough it was all threw the rocks when I cleaned the tank right after snapping this picture. And it was to late for Vincent :(
I also wanted to add my experience with the pineapple and squidwards house... I have both in my sons tank. I've had them in there since early November and they have been fine. No pealing, no weird smell, no slime. They must have fixed their issue? The only thing I had to do was file around the holes a little to get rid of a few sharp edges.
glad I read this thread. I have seen some around my pet store but opted not to get them and choose more important things that I needed (food and conditioner). I've been thinking about going back and getting them/ considered getting them lots of other times. once I was standing in the check out like with one and then changed my mind last minute because I couldn't find my phone