Originally Posted by TheOscar
I've has these river rocks in several tanks in the past.. Recently that have like rust on them.. I removed,, just wondering what causes this
I use the vinegar test on the rocks I put into my tanks. This one may not be safe to use. Let the piece dry. Then, put a few drops of vinegar on it. If there's a reaction of any kind, then don't use it. If there's no change, then rinse it well and if you want, put it back into the tank.