This part is disturbing for anyone thinking about using these pads in a lower pH tank:
"Props go out to Chris Derrick
Quote:
I went and purchased a box of 20 for my 4 emp 400 hanging out back because I thought it was a great idea. I got to reading on the box and it says in bold print NOT FOR AQUARIUM USE! So I called 3M the company that makes scotch brite and talked to a rep about why this is and he told me it will kill the fish because they use aluminum oxide in the material to help it clean stuff better. I was so glad I didn't use it on my new wild caught tropheus tank and thought I would pass it along here maybe save some one else's fish also! Now lets find out a new idea on what to use to save money on these filters. Thanks and hope this helps.
They do contain some Al2O3, and it is toxic to fish in acidic water. It's also an ingredient in blasting sand. They should be safe for use in alkaline waters, I believe.
http://www.cichlid-forum.com/articles/rock_metals.php
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Heavy metals (lead, zinc, copper, cadmium, etc etc and even iron) are toxic for fish, inverts, and mammals, including us, when they reach certain-enormously varying-concentrations. In the case of fish, such metals are primarily dangerous in their free ionic form in the water where they are available for uptake by the fish metabolism.
In the form of compounds, such as oxides, they are inert and not free for metabolic uptake. For example water conditioners which 'detoxify' heavy metals actually bind them into compounds which cannot be absorbed by the fish
In water of neutral or alkaline pH heavy metals normally remain locked into such compounds and remain inert.
Acidic water (pH less than 7) on the other hand activates these metals and renders them potentially dangerous."
