I would love to see this in a tank...black especially.Sand is much lighter than plastic pellets... again these are not polypropylene. They are a ppe plastic. They will sink and not be sucked up easily compared to sand. I mean sand is much much lighter and notorious for being sucked up into filters.
I work at a plastic injection molding facility. I can get my hands on some plastic pellets and I was curious if this would be ok for rays. I would cut down on debris in the filter and also I could run a powerhead over it without disturbing it too much. I could keep the substrate clean but yet light enough I believe a ray could burrow in it. The link below will show you what it looks like. I am going to use a natural color like a black or white or tan. All i have to do is make sure the specific gravity is over 1.0. Please let me know if you see any issues with this. I am planning on keeping a ray. I doubt anybody has used this but if you have please chime in. Thanks
https://www.google.com/search?q=raw...KEwjm967evLjJAhUBXh4KHUEsBfoQ_AUIBygC#imgrc=_
PVC and Garden hoses are made of the same kind of plastic Polyvinyl Chloride. I mentioned in my previous post that plasticizers aren't used in all plastics however Polyvinyl Chloride is one kind of plastic that does use plasticizers. I also mentioned that many of the effects of leached chemical from plastics remain unknown. One known effect however is that BPA( Bisphenol A) which is leached by many plastics and in people mimics estrogen causing hormonal imbalances. These endocrine disruptors cause a slew of health problems caused by the imbalance including liver cancer. Water passing through Garden hoses has been found to carry 20% more BPA then the National Science Foundation considers safe. Again these studies are focused on people and the effects on fish are currently unknown.On the subject of fish eating plastic, most will be able to pass an occasional indigestible item but a percentage will clog intestines and other GI issues.
I also have been using garden hoses and small sections of PVC for years, if anyone has info on the dangers of doing so; I'm interested to hear.