I am aware that copper is required as a micronutrient and I was not sure if copper was a heavy metal but when I looked at Heavy Metal Toxicity: Online Reference for Health Concerns they said it was as do many others so I called it one, I did intend for it to be a word of caution of the build up not that it would be the same as using Roundup Weed Killer but I can see where I could have been more clear. And as far as weather or not it is algae seeing as it is
Are you using regular tap water? A friend had similar issue when he didn't let the chlorine dissipate. Try leaving the water standing for 24hrs before you use it.
I am using city water that goes through an RO filtration system.
That being the case, its not what my friend had going on in your tank. Is there any odor? If it smells really bad (like dirty sweat socks or something rancid) you might be getting rot problems. Hydrogen peroxide, or SM90 might help.
Update on the slime: When I first posted, I had an older membrane in my RO filter. Since then, I've installed a new membrane, and the slime is either gone, or so greatly reduced that I'm not noticing it now when I do water changes. So maybe it was related to the chlorine issue?
Don't know what this means, but it's an interesting development. Thanks, everyone, for your input!