So I've just inherited a freshwater fish tank and haven't studied them since I was little. I'd like to put this piece of coral rock that washed up a few years ago and any others I might find as soon as it gets warm enough to get in the Ocean and put them in. Is this safe, what are the precautionary steps and one last thing. What are some cool looking fish that can live with silver dollars. The tank has three and they're kinda big so I either gotta get fish that will play well or donate them to my neighbors koi pond.